MCP Accessibility Scanner
MCP Accessibility Scanner 🔍
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A powerful Model Context Protocol (MCP) server that provides automated web accessibility scanning and browser automation using Playwright and Axe-core. This server enables LLMs to perform WCAG compliance checks, interact with web pages, manage persistent browser sessions, and generate detailed accessibility reports with visual annotations.
Related MCP server: Accessibility Testing MCP
Features
Accessibility Scanning
✅ Full WCAG 2.0/2.1/2.2 compliance checking (A, AA, AAA levels)
📄 Detailed JSON reports with remediation guidance
🎯 Support for specific violation categories (color contrast, ARIA, forms, keyboard navigation, etc.)
Browser Automation
🖱️ Click, hover, and drag elements using accessibility snapshots
⌨️ Type text and handle keyboard inputs
🔍 Capture page snapshots to discover all interactive elements
📸 Take screenshots and save PDFs
🎯 Support for both element-based and coordinate-based interactions
Advanced Features
📑 Tab management for multi-page workflows
🌐 Monitor console messages and network requests
⏱️ Wait for dynamic content to load
📁 Handle file uploads and browser dialogs
🔄 Navigate through browser history
Installation
You can install the package using any of these methods:
Using npm:
npm install -g mcp-accessibility-scannerInstallation with Docker
A pre-built image is available on Docker Hub. The image includes Chromium and is pre-configured for containerized use — no extra flags needed.
Pull from Docker Hub:
docker pull justasmonkev/mcp-accessibility-scannerClaude Code
claude mcp add mcp-accessibility-scanner -s user -- docker run -i --rm justasmonkev/mcp-accessibility-scannerTo persist screenshots and reports on your host, add a volume mount:
claude mcp add mcp-accessibility-scanner -s user \
-- docker run -i --rm -v /tmp/mcp-output:/app/output justasmonkev/mcp-accessibility-scannerWithout the -v mount, output files only exist inside the container and are lost when it exits.
Docker Compose
docker compose up -dBuild from source
docker build -t mcp-accessibility-scanner .Docker smoke test
npm run test:dockerInstallation in VS Code
Install the Accessibility Scanner in VS Code using the VS Code CLI:
For VS Code:
code --add-mcp '{"name":"accessibility-scanner","command":"npx","args":["mcp-accessibility-scanner"]}'For VS Code Insiders:
code-insiders --add-mcp '{"name":"accessibility-scanner","command":"npx","args":["mcp-accessibility-scanner"]}'CLI Modes
The scanner can run in two modes depending on how you use it.
MCP server (default, no subcommand)
When launched without a subcommand, the process starts an MCP server that communicates over stdio. This is the mode used by MCP clients such as Claude Desktop, VS Code, and Claude Code -- you should never need to run it by hand.
npx mcp-accessibility-scanner # starts the MCP server (stdio)All of the MCP client configuration examples in this README already use this default mode.
Interactive REPL (interactive subcommand)
For manual terminal use, the interactive subcommand starts a readline REPL where you can call any tool directly:
$ npx mcp-accessibility-scanner interactive
Interactive mode. Type "<tool-name> <json>" to call a tool. Ctrl+D to exit.
> browser_navigate {"url": "https://example.com"}
> scan_page {"violationsTag": ["wcag21aa"]}
> audit_keyboard {"maxTabs": 30}Each line is <tool-name> <json-arguments>. Omit the JSON to pass {}.
Global browser connection flags still apply here, for example npx mcp-accessibility-scanner --extension interactive.
Discovering available tools (list-tools subcommand)
To print every tool name and its description:
npx mcp-accessibility-scanner list-toolsNote: Tool names like
browser_navigateandscan_pageare MCP tool identifiers (and REPL commands in interactive mode). They are not shell subcommands -- you cannot runnpx mcp-accessibility-scanner browser_navigate.
Configuration
Here's the Claude Desktop configuration:
{
"mcpServers": {
"accessibility-scanner": {
"command": "npx",
"args": ["-y", "mcp-accessibility-scanner"]
}
}
}Advanced Configuration
You can pass a configuration file to customize Playwright behavior:
{
"mcpServers": {
"accessibility-scanner": {
"command": "npx",
"args": ["-y", "mcp-accessibility-scanner", "--config", "/path/to/config.json"]
}
}
}Configuration Options
Create a config.json file with the following options:
{
"browser": {
"browserName": "chromium",
"launchOptions": {
"headless": true,
"channel": "chrome"
},
"cdpLaunch": {
"command": "open",
"args": ["-a", "Slack", "--args", "--remote-debugging-port={port}"],
"startupTimeoutMs": 30000
}
},
"timeouts": {
"navigationTimeout": 60000,
"defaultTimeout": 5000
},
"network": {
"allowedOrigins": ["example.com", "trusted-site.com"],
"blockedOrigins": ["ads.example.com"]
}
}Available Options:
browser.browserName: Browser to use (chromium,firefox,webkit)browser.launchOptions.headless: Run browser in headless mode (default:trueon Linux without display,falseotherwise)browser.launchOptions.channel: Browser channel (chrome,chrome-beta,msedge, etc.)browser.cdpEndpoint: Attach to an already-running Chromium-family app with CDP enabledbrowser.cdpLaunch: Launch a Chromium-family desktop app with CDP enabled, wait for the endpoint, and manage the child process lifecycletimeouts.navigationTimeout: Maximum time for page navigation in milliseconds (default:60000)timeouts.defaultTimeout: Default timeout for Playwright operations in milliseconds (default:5000)network.allowedOrigins: List of origins to allow (blocks all others if specified)network.blockedOrigins: List of origins to block
CLI equivalents are also available: --cdp-launch-command, --cdp-launch-args, --cdp-launch-cwd, --cdp-launch-port, and --cdp-launch-startup-timeout.
Available Tools
The MCP server provides comprehensive browser automation and accessibility scanning tools:
Core Accessibility Tool
scan_page
Performs a comprehensive accessibility scan on the current page using Axe-core.
Parameters:
violationsTag: Array of WCAG/violation tags to check
Supported Violation Tags:
WCAG standards:
wcag2a,wcag2aa,wcag2aaa,wcag21a,wcag21aa,wcag21aaa,wcag22a,wcag22aa,wcag22aaaSection 508:
section508Categories:
cat.aria,cat.color,cat.forms,cat.keyboard,cat.language,cat.name-role-value,cat.parsing,cat.semantics,cat.sensory-and-visual-cues,cat.structure,cat.tables,cat.text-alternatives,cat.time-and-media
Audit Tools
audit_site
Crawls and scans multiple internal pages, then aggregates violations across the site.
Default strategy: link-based BFS from the current URL
Supports
links,nav,sitemap, andprovidedURL strategiesAlways writes a JSON report (default filename:
audit-site-{timestamp}.json)
Example flow:
1. Navigate to your site homepage with browser_navigate
2. Run audit_site with maxPages: 25 and maxDepth: 2
3. Review the report path returned by the tool (written to the MCP output directory)scan_page_matrix
Runs Axe scans on the same page across viewport/media/zoom variants and compares deltas against baseline.
Default variants: baseline, mobile, desktop, forced-colors, reduced-motion, zoom-200
Supports custom variants and optional reload between variants
Always writes a JSON report (default filename:
scan-matrix-{timestamp}.json)
Example flow:
1. Navigate to a page state you want to validate
2. Run scan_page_matrix with defaults (or provide custom variants)
3. Review per-variant deltas and open the generated JSON report pathaudit_keyboard
Audits real keyboard focus behavior by pressing Tab (and optional Shift+Tab) with practical heuristics.
Checks skip links, focus visibility, focus jumps, and possible focus traps
Optional issue screenshots (
screenshotOnIssue)Always writes a JSON report (default filename:
audit-keyboard-{timestamp}.json)
Example flow:
1. Navigate to the target page and let it fully load
2. Run audit_keyboard with maxTabs: 50
3. Review focus findings and open the generated JSON report pathNavigation Tools
browser_navigate
Navigate to a URL.
Parameters:
url(string)
browser_navigate_back
Go back to the previous page.
browser_navigate_forward
Go forward to the next page.
Page Interaction Tools
browser_snapshot
Capture accessibility snapshot of the current page (better than screenshot for analysis).
browser_click
Perform click on a web page element.
Parameters:
element(description),ref(element reference),doubleClick(optional)
browser_type
Type text into editable element.
Parameters:
element,ref,text,submit(optional),slowly(optional)
browser_hover
Hover over element on page.
Parameters:
element,ref
browser_drag
Perform drag and drop between two elements.
Parameters:
startElement,startRef,endElement,endRef
browser_select_option
Select an option in a dropdown.
Parameters:
element,ref,values(array)
browser_press_key
Press a key on the keyboard.
Parameters:
key(e.g., 'ArrowLeft' or 'a')
Screenshot & Visual Tools
browser_take_screenshot
Take a screenshot of the current page.
Parameters:
raw(optional),filename(optional),element(optional),ref(optional)
browser_pdf_save
Save page as PDF.
Parameters:
filename(optional, defaults topage-{timestamp}.pdf)
Browser Management
browser_close
Close the page.
browser_resize
Resize the browser window.
Parameters:
width,height
Tab Management
browser_tab_list
List all open browser tabs.
browser_tab_new
Open a new tab.
Parameters:
url(optional)
browser_tab_select
Select a tab by index.
Parameters:
index
browser_tab_close
Close a tab.
Parameters:
index(optional, closes current tab if not provided)
Information & Monitoring Tools
browser_console_messages
Returns all console messages from the page.
browser_network_requests
Returns all network requests since loading the page.
Utility Tools
browser_wait_for
Wait for text to appear/disappear or time to pass.
Parameters:
time(optional),text(optional),textGone(optional)
browser_handle_dialog
Handle browser dialogs (alerts, confirms, prompts).
Parameters:
accept(boolean),promptText(optional)
browser_file_upload
Upload files to the page.
Parameters:
paths(array of absolute file paths)
Vision Mode Tools (Coordinate-based Interaction)
browser_screen_capture
Take a screenshot for coordinate-based interaction.
browser_screen_move_mouse
Move mouse to specific coordinates.
Parameters:
element,x,y
browser_screen_click
Click at specific coordinates.
Parameters:
element,x,y
browser_screen_drag
Drag from one coordinate to another.
Parameters:
element,startX,startY,endX,endY
browser_screen_type
Type text (coordinate-independent).
Parameters:
text,submit(optional)
Usage Examples
Basic Accessibility Scan
1. Navigate to example.com using browser_navigate
2. Run scan_page with violationsTag: ["wcag21aa"]Color Contrast Check
1. Use browser_navigate to go to example.com
2. Run scan_page with violationsTag: ["cat.color"]Multi-step Workflow
1. Navigate to example.com with browser_navigate
2. Take a browser_snapshot to see available elements
3. Click the "Sign In" button using browser_click
4. Type "user@example.com" using browser_type
5. Run scan_page on the login page
6. Take a browser_take_screenshot to capture the final statePage Analysis
1. Navigate to example.com
2. Use browser_snapshot to capture all interactive elements
3. Review console messages with browser_console_messages
4. Check network activity with browser_network_requestsTab Management
1. Open a new tab with browser_tab_new
2. Navigate to different pages in each tab
3. Switch between tabs using browser_tab_select
4. List all tabs with browser_tab_listWaiting for Dynamic Content
1. Navigate to a page
2. Use browser_wait_for to wait for specific text to appear
3. Interact with the dynamically loaded contentNote: Most interaction tools require element references from browser_snapshot. Always capture a snapshot before attempting to interact with page elements.
Development
Clone and set up the project:
git clone https://github.com/JustasMonkev/mcp-accessibility-scanner.git
cd mcp-accessibility-scanner
npm installLicense
MIT
Available Tools
25 toolsbrowser_clickBDestructive
Perform click on a web page
| Name | Required | Description | Default |
|---|---|---|---|
| doubleClick | No | Whether to perform a double click instead of a single click | |
| element | Yes | Human-readable element description used to obtain permission to interact with the element | |
| ref | Yes | Exact target element reference from the page snapshot |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate destructiveHint=true and readOnlyHint=false, which already signal this is a write operation that can change page state. The description adds no behavioral context beyond this, such as potential side effects (e.g., navigation, form submission) or error conditions. It doesn't contradict annotations, but offers minimal extra insight.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence with no wasted words. It's front-loaded with the core action, making it easy to scan and understand quickly. Every word earns its place by conveying the essential purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (interactive, destructive) and lack of output schema, the description is minimal. It covers the basic action but omits details like return values, error handling, or dependencies on other tools (e.g., browser_snapshot for ref). With annotations providing safety cues, it's adequate but leaves gaps for effective use.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the schema fully documents all parameters (doubleClick, element, ref). The description adds no additional meaning about parameters, such as explaining the relationship between element and ref or when to use doubleClick. This meets the baseline for high schema coverage.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Perform click') and resource ('on a web page'), which is specific and unambiguous. However, it doesn't distinguish this from sibling tools like browser_hover or browser_drag, which also involve element interactions, so it doesn't reach the highest score for sibling differentiation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. For example, it doesn't mention when to choose browser_click over browser_double_click (implied via parameter) or browser_hover, nor does it specify prerequisites like needing a browser session or element reference from browser_snapshot.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_closeBRead-only
Close the page
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, covering safety and scope. The description adds minimal behavioral context beyond this, not explaining what 'close' entails (e.g., whether it terminates a session or just a tab) or any side effects, but doesn't contradict annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise with 'Close the page'—a single, front-loaded sentence that directly conveys the action without any wasted words, making it efficient and easy to parse.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (0 parameters, no output schema) and annotations covering key behavioral traits, the description is minimally adequate. However, it lacks details on what 'close' means operationally (e.g., closes current tab vs. entire browser) and how it interacts with siblings, leaving some contextual gaps.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 0 parameters and 100% schema coverage, the baseline is 4 as no parameter documentation is needed. The description doesn't add parameter details, which is appropriate given the empty schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Close the page' clearly states the action (close) and target (the page), which is specific and unambiguous. However, it doesn't differentiate from sibling 'browser_tab_close' which might have similar functionality, preventing a perfect score.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives like 'browser_tab_close' or when not to use it (e.g., if no page is open). It lacks context about prerequisites or exclusions, leaving usage unclear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_console_messagesARead-only
Returns all console messages
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=true, destructiveHint=false, and openWorldHint=true, indicating a safe read operation with potentially unbounded results. The description adds value by specifying 'all console messages' (implying comprehensive retrieval), which complements the openWorldHint about unbounded data. No contradiction with annotations, and it provides useful context about scope.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Extremely concise with a single sentence that directly states the tool's function. No unnecessary words or structural fluff. Every word earns its place by conveying essential information efficiently.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (0 parameters, read-only operation with annotations), the description is minimally adequate. However, it lacks details about what 'console messages' includes (e.g., logs, errors, warnings), whether it's real-time or historical, and there's no output schema to clarify return values. For a tool that retrieves data, more context about the data format would be helpful.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There are 0 parameters, and schema description coverage is 100%. The description doesn't need to explain parameters, and it appropriately doesn't mention any. A baseline of 4 is appropriate for a zero-parameter tool where the schema fully covers the input structure.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Returns all console messages' clearly states the action (returns) and resource (console messages). It distinguishes from most siblings that perform browser interactions (click, navigate, type) but doesn't explicitly differentiate from browser_network_requests which also returns data. The purpose is specific but could be more precise about what 'console messages' refers to.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool versus alternatives. The description doesn't mention prerequisites (e.g., needing an active browser session), appropriate contexts, or when other tools might be more suitable. It's a standalone statement with no usage context.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_dragBDestructive
Perform drag and drop between two elements
| Name | Required | Description | Default |
|---|---|---|---|
| endElement | Yes | Human-readable target element description used to obtain the permission to interact with the element | |
| endRef | Yes | Exact target element reference from the page snapshot | |
| startElement | Yes | Human-readable source element description used to obtain the permission to interact with the element | |
| startRef | Yes | Exact source element reference from the page snapshot |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide key behavioral hints: destructiveHint=true (indicating potential changes), readOnlyHint=false (confirms it's a mutation), and openWorldHint=true (suggests dynamic environment). The description adds minimal context beyond this, stating the action but not elaborating on effects like UI state changes or error conditions. No contradiction with annotations exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence that directly states the tool's purpose without unnecessary words. It is front-loaded and wastes no space, making it easy to parse quickly.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the complexity of a drag-and-drop operation in a browser context, the description is minimal. Annotations cover safety and environment aspects, but no output schema exists, and the description doesn't address return values, error handling, or interaction nuances. It's adequate but leaves gaps for a tool with destructive potential.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with clear documentation for all four parameters (startElement, startRef, endElement, endRef). The description adds no additional parameter semantics, such as explaining the relationship between 'element' and 'ref' parameters or usage examples. Baseline score of 3 is appropriate given high schema coverage.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('perform drag and drop') and specifies the relationship ('between two elements'), which is more specific than just the tool name. However, it doesn't explicitly differentiate from sibling tools like browser_click or browser_hover that also involve element interaction, though the drag-and-drop action is distinct.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives like browser_click or browser_hover for similar element interactions. It lacks context about prerequisites (e.g., needing element references from a snapshot) or scenarios where drag-and-drop is appropriate over other methods.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_file_uploadBDestructive
Upload one or multiple files
| Name | Required | Description | Default |
|---|---|---|---|
| paths | Yes | The absolute paths to the files to upload. Can be a single file or multiple files. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate this is a destructive, non-read-only operation with open-world behavior. The description adds no behavioral context beyond what annotations provide (e.g., no details on upload destinations, error handling, or file size limits), but it doesn't contradict annotations either.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise at just four words, front-loading the core action and resource with zero wasted language. Every word earns its place by clearly communicating the essential function.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a destructive tool with no output schema, the description is minimally complete but lacks important context. It doesn't explain what happens after upload, potential side effects, or error conditions, leaving gaps despite good annotations covering basic safety profile.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 100% schema description coverage, the input schema fully documents the 'paths' parameter. The description mentions 'one or multiple files' which aligns with the schema but adds no additional semantic context beyond what's already in the structured data.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('upload') and resource ('one or multiple files'), making the purpose immediately understandable. However, it doesn't differentiate this tool from potential sibling upload tools (though none exist in the provided sibling list), which prevents a perfect score.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives or prerequisites. It doesn't mention context like browser state requirements or when other browser tools might be more appropriate, leaving the agent with minimal usage direction.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_handle_dialogCDestructive
Handle a dialog
| Name | Required | Description | Default |
|---|---|---|---|
| accept | Yes | Whether to accept the dialog. | |
| promptText | No | The text of the prompt in case of a prompt dialog. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=false, openWorldHint=true, and destructiveHint=true, indicating this is a mutable, open-ended, and potentially destructive operation. The description doesn't contradict these annotations, but it adds minimal context beyond them—it vaguely implies interaction with dialogs without detailing what 'handle' entails (e.g., accepting/dismissing, providing input). For a tool with annotations covering safety and scope, the description adds some value but lacks rich behavioral details like side effects or error conditions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise with just three words, front-loaded and free of unnecessary information. Every word ('Handle a dialog') directly relates to the tool's function, though it's under-specified. There's no wasted text, making it efficient in structure despite its content gaps.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (handling dialogs with potential destruction), lack of output schema, and rich annotations, the description is incomplete. It doesn't explain what a 'dialog' is in this context, what happens when accepted or dismissed, or the return behavior. The annotations provide safety hints, but the description fails to add necessary context for effective use, leaving significant gaps in understanding.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with clear documentation for both parameters: 'accept' (boolean for accepting the dialog) and 'promptText' (string for prompt dialog text). The description adds no meaning beyond the schema—it doesn't explain how these parameters interact or provide examples of usage. Given the high schema coverage, the baseline score of 3 is appropriate, as the schema handles parameter documentation adequately.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Handle a dialog' is a tautology that restates the tool name without specifying what 'handle' means or what type of dialog is involved. It doesn't distinguish this tool from sibling browser tools like browser_click or browser_press_key, which also handle interactions. The description lacks a specific verb-resource combination that clarifies the action.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention what triggers a dialog (e.g., alerts, prompts, confirmations) or when other tools like browser_click might be more appropriate. There's no context about prerequisites or exclusions, leaving the agent with no usage direction.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_hoverBRead-only
Hover over element on page
| Name | Required | Description | Default |
|---|---|---|---|
| element | Yes | Human-readable element description used to obtain permission to interact with the element | |
| ref | Yes | Exact target element reference from the page snapshot |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, indicating a safe, non-destructive operation with potential for dynamic content. The description adds minimal behavioral context beyond this, as 'hover' implies a UI interaction but doesn't detail effects like triggering events or visual feedback. It doesn't contradict annotations, so it earns a baseline score for adding some value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description 'Hover over element on page' is extremely concise and front-loaded, consisting of a single, direct sentence that efficiently communicates the core action. Every word earns its place with no redundancy or unnecessary elaboration, making it easy to parse quickly.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's moderate complexity (interactive UI action), rich annotations (readOnlyHint, openWorldHint), and no output schema, the description is minimally complete. It states what the tool does but lacks details on outcomes (e.g., what hovering achieves), error conditions, or integration with sibling tools. This leaves gaps for an agent to fully leverage the tool in context.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with clear documentation for both parameters: 'element' as a human-readable description for permissions and 'ref' as an exact target reference. The description adds no additional parameter semantics beyond what the schema provides, such as examples or interaction details, so it meets the baseline for high schema coverage without enhancing understanding.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Hover over element on page' clearly states the action (hover) and target (element on page), making the purpose immediately understandable. It uses a specific verb+resource pattern, though it doesn't explicitly differentiate from sibling tools like browser_click or browser_press_key, which prevents a perfect score.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention scenarios where hovering is appropriate (e.g., triggering dropdowns, tooltips) or when to avoid it, nor does it reference sibling tools like browser_click for different interactions. This lack of contextual usage information is a significant gap.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_installADestructive
Install the browser specified in the config. Call this if you get an error about the browser not being installed.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate destructiveHint=true and readOnlyHint=false, which the description aligns with by implying installation (a write operation). The description adds valuable context beyond annotations by specifying it's for resolving installation errors, which helps the agent understand when this destructive action is appropriate.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is two concise sentences that directly address the tool's purpose and usage scenario. Every word serves a clear function, with no redundant or unnecessary information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has 0 parameters, no output schema, and annotations cover key behavioral aspects (destructive, not read-only), the description provides sufficient context by explaining what it does and when to use it. It could slightly improve by mentioning what 'config' refers to, but it's adequate for this simple tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has 0 parameters with 100% coverage, so no parameter documentation is needed. The description appropriately doesn't discuss parameters, maintaining focus on the tool's purpose and usage context.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Install') and target ('browser specified in the config'), making the purpose understandable. However, it doesn't explicitly differentiate from sibling tools like browser_click or browser_navigate, which perform different browser operations rather than installation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides explicit guidance on when to use this tool: 'Call this if you get an error about the browser not being installed.' This clearly defines the trigger condition and context for usage, with no misleading information.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_network_requestsARead-only
Returns all network requests since loading the page
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, covering safety and scope. The description adds useful context by specifying 'since loading the page,' which clarifies the temporal scope of data returned, enhancing behavioral understanding beyond annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, clear sentence that efficiently conveys the core functionality without any wasted words. It's front-loaded with the main action and resource, making it highly concise and well-structured.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (0 parameters, no output schema) and rich annotations, the description is adequate but has gaps. It lacks details on output format (e.g., structure of returned requests) and doesn't address potential limitations like data volume or browser state requirements, making it minimally viable.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 0 parameters and 100% schema description coverage, there's no need for parameter details in the description. The baseline for zero parameters is 4, as the description appropriately focuses on the tool's function without redundant parameter explanations.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Returns') and resource ('all network requests since loading the page'), making the purpose understandable. However, it doesn't explicitly differentiate from siblings like browser_console_messages or browser_tab_list, which also retrieve browser data but for different resources.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an active browser page), exclusions, or how it relates to siblings like browser_console_messages for different data types, leaving usage context unclear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_pdf_saveBRead-only
Save page as PDF
| Name | Required | Description | Default |
|---|---|---|---|
| filename | No | File name to save the pdf to. Defaults to `page-{timestamp}.pdf` if not specified. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=true, destructiveHint=false, and openWorldHint=true, indicating a safe, non-destructive operation with flexible inputs. The description adds minimal behavioral context beyond this—it implies saving the current page but doesn't specify what 'page' means (e.g., current tab, entire page vs. viewport) or any limitations (e.g., file size, format constraints). No contradiction with annotations exists, but the description under-leverages the opportunity to clarify behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise at three words, front-loading the core action without unnecessary elaboration. Every word ('Save', 'page', 'PDF') directly contributes to understanding the tool's function, making it efficient and easy to parse.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the lack of output schema and the tool's potential complexity (saving a PDF involves rendering and file I/O), the description is insufficient. It doesn't address what happens on success/failure, where the PDF is saved, or any dependencies (e.g., requires a loaded page). With annotations covering safety but not operational details, more context is needed for reliable use.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 100% schema description coverage for the single parameter 'filename', the schema fully documents its purpose and default behavior. The description adds no parameter-specific information beyond the tool's overall function, so it meets the baseline of 3 where the schema handles the heavy lifting without extra value from the description.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Save page as PDF' clearly states the verb ('Save') and resource ('page as PDF'), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'browser_take_screenshot' or 'browser_snapshot' that might also capture page content, leaving room for confusion about when to choose this specific PDF-saving function.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., requires an active browser page), exclusions (e.g., can't save dynamic content), or comparisons to siblings like 'browser_take_screenshot' for image capture or 'browser_snapshot' for other formats. This lack of context could lead to inappropriate tool selection.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_press_keyBDestructive
Press a key on the keyboard
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | Name of the key to press or a character to generate, such as `ArrowLeft` or `a` |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide key behavioral hints (destructiveHint: true, readOnlyHint: false, openWorldHint: true), but the description adds minimal context beyond stating the action. It doesn't elaborate on what 'destructive' means in this context (e.g., potential side effects like triggering events) or mention rate limits, though annotations cover the safety profile adequately.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, clear sentence with zero wasted words. It's front-loaded with the core action, making it highly efficient and easy to parse, which is ideal for a simple tool.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (1 parameter, no output schema) and rich annotations, the description is minimally adequate. However, it lacks details on return values or error conditions, which could be helpful despite the annotations covering basic behavior.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 100% schema description coverage, the input schema fully documents the single 'key' parameter, including examples like 'ArrowLeft' or 'a'. The description adds no additional parameter information, so it meets the baseline for high schema coverage without compensating value.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Press a key on the keyboard' clearly states the action (press) and resource (key on keyboard), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'browser_type' which might have overlapping functionality, preventing a perfect score.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives like 'browser_type' or 'browser_click'. It lacks context about specific scenarios, prerequisites, or exclusions, leaving the agent to infer usage from the tool name alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_resizeBRead-only
Resize the browser window
| Name | Required | Description | Default |
|---|---|---|---|
| height | Yes | Height of the browser window | |
| width | Yes | Width of the browser window |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide key behavioral hints: readOnlyHint=true and destructiveHint=false indicate it's a safe, non-destructive operation, and openWorldHint=true suggests it can be used in various contexts. The description adds minimal context beyond this—it doesn't specify if resizing affects page rendering, requires specific permissions, or has side effects. No contradiction with annotations exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, direct sentence with zero wasted words. It's front-loaded with the core action, making it highly efficient. Every part of the sentence ('Resize the browser window') contributes essential information without redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (2 simple parameters) and rich annotations (covering safety and scope), the description is minimally adequate. However, with no output schema, it doesn't explain what happens after resizing (e.g., success confirmation or error handling). For a browser interaction tool, more context on effects would be helpful.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has 100% description coverage, with clear parameter definitions for 'width' and 'height'. The description adds no additional semantic context beyond implying these parameters are required for resizing. It doesn't explain units (e.g., pixels), valid ranges, or default behaviors, so it relies entirely on the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb ('Resize') and resource ('the browser window'), making the purpose immediately understandable. It distinguishes itself from siblings like browser_close or browser_take_screenshot by focusing on window dimensions. However, it doesn't explicitly differentiate from all siblings (e.g., browser_snapshot might also involve window manipulation).
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an active browser session), exclusions, or related tools. For example, it doesn't clarify if this should be used instead of browser_tab_new for window management or how it interacts with browser_navigate.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_select_optionBDestructive
Select an option in a dropdown
| Name | Required | Description | Default |
|---|---|---|---|
| element | Yes | Human-readable element description used to obtain permission to interact with the element | |
| ref | Yes | Exact target element reference from the page snapshot | |
| values | Yes | Array of values to select in the dropdown. This can be a single value or multiple values. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate destructiveHint=true and readOnlyHint=false, which the description doesn't contradict. However, the description adds no behavioral context beyond the annotations—it doesn't explain what 'destructive' means here (e.g., changes UI state), rate limits, or error handling. With annotations covering safety, a 3 reflects minimal added value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence with zero waste—it directly states the tool's purpose without redundancy. It's appropriately sized for a simple action tool and front-loaded with essential information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (moderate, with destructive behavior), rich annotations, and no output schema, the description is minimally adequate. It covers the basic action but lacks details on outcomes, error cases, or integration with siblings like browser_snapshot for obtaining 'ref'. With annotations, it meets a baseline but could be more informative.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so parameters are fully documented in the schema. The description adds no additional meaning beyond implying dropdown interaction, which is already clear from the tool name. Baseline 3 is appropriate as the schema does the heavy lifting.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Select an option in a dropdown' clearly states the action (select) and target (dropdown), distinguishing it from siblings like browser_click or browser_type. However, it doesn't explicitly differentiate from browser_handle_dialog which might also involve dropdowns, making it slightly less specific than a perfect 5.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., requiring a page snapshot), exclusions, or comparisons to siblings like browser_click for non-dropdown interactions, leaving the agent to infer usage from context alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_snapshotBRead-only
Capture accessibility snapshot of the current page, this is better than screenshot
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, covering safety and scope. The description adds value by specifying it captures an 'accessibility snapshot' (implying structured data like ARIA attributes) rather than a visual image, which is useful context beyond annotations. However, it doesn't detail output format or potential limitations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence that front-loads the core purpose ('Capture accessibility snapshot of the current page') and adds a brief comparative note. Every word serves a purpose, with no wasted text, making it highly concise and well-structured.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 0 parameters, rich annotations (readOnlyHint, destructiveHint, openWorldHint), and no output schema, the description is adequate but could be more complete. It explains what the tool does but doesn't clarify the output (e.g., what an 'accessibility snapshot' contains) or tie into the sibling tools effectively, leaving some gaps in context.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There are 0 parameters, and schema description coverage is 100%, so no parameter documentation is needed. The description appropriately doesn't discuss parameters, earning a baseline score of 4 for not adding unnecessary information.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb ('capture') and resource ('accessibility snapshot of the current page'), making the purpose specific and understandable. However, it doesn't explicitly distinguish this from the sibling 'browser_take_screenshot' tool beyond saying 'this is better than screenshot,' which is somewhat vague rather than a clear differentiation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides minimal guidance by implying this tool is preferable to 'browser_take_screenshot' for accessibility purposes, but it doesn't specify when to use it (e.g., for accessibility testing vs. visual capture) or when not to use it. No explicit alternatives or prerequisites are mentioned, leaving usage context unclear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_tab_closeCDestructive
Close a tab
| Name | Required | Description | Default |
|---|---|---|---|
| index | No | The index of the tab to close. Closes current tab if not provided. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide key behavioral hints: destructiveHint=true (indicating data loss) and openWorldHint=true (suggesting external effects). The description adds no behavioral context beyond 'Close a tab', such as what happens to unsaved data or if confirmation is needed. It doesn't contradict annotations, but adds minimal value given the annotations cover safety and scope.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise ('Close a tab') with zero wasted words, making it front-loaded and easy to parse. It efficiently conveys the core action without unnecessary detail, though this brevity contributes to gaps in other dimensions.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's destructive nature (per annotations) and lack of output schema, the description is incomplete. It doesn't explain return values, error conditions, or behavioral nuances like what happens after closing (e.g., focus shift). For a destructive tool with no output schema, more context is needed to guide safe usage.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with the parameter 'index' fully documented in the schema (closes current tab if not provided). The description adds no parameter semantics beyond what the schema provides, so it meets the baseline of 3 for high schema coverage without extra value.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Close a tab' states the action (close) and resource (tab), but it's vague about scope and doesn't differentiate from sibling tools like 'browser_close' (which likely closes the entire browser). It doesn't specify whether this closes tabs in a browser context or another environment, leaving ambiguity.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance is provided on when to use this tool versus alternatives. It doesn't mention siblings like 'browser_tab_list' (to list tabs before closing) or 'browser_tab_select' (to select a tab first), nor does it specify prerequisites such as needing an open browser or tab. Usage context is implied but not explicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_tab_listBRead-only
List browser tabs
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint=true, destructiveHint=false, and openWorldHint=true, indicating this is a safe, read-only operation. The description adds minimal behavioral context beyond this, as it doesn't specify what information is listed (e.g., tab titles, URLs) or any constraints like performance implications. It doesn't contradict annotations, but adds little value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description 'List browser tabs' is extremely concise and front-loaded, consisting of just three words that directly convey the core action. There's no wasted language or unnecessary elaboration, making it efficient for an AI agent to parse.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (0 parameters, no output schema) and rich annotations, the description is minimally adequate. However, it lacks details on what the output includes (e.g., tab IDs, titles) or usage context, which could be helpful for an agent. The annotations cover safety, but the description doesn't fully compensate for the missing output schema.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has 0 parameters with 100% coverage, so no parameter documentation is needed. The description doesn't add parameter information, which is appropriate here. A baseline of 4 is applied since no parameters exist, and the description doesn't introduce confusion.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'List browser tabs' clearly states the verb ('List') and resource ('browser tabs'), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'browser_tab_select' or 'browser_tab_close', which also involve tabs but perform different actions, so it lacks sibling differentiation.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. For example, it doesn't mention if this is for getting current tab information or all tabs, or how it relates to siblings like 'browser_tab_select'. There's no explicit context or exclusions provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_tab_newARead-only
Open a new tab
| Name | Required | Description | Default |
|---|---|---|---|
| url | No | The URL to navigate to in the new tab. If not provided, the new tab will be blank. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint=true, destructiveHint=false, and openWorldHint=true, indicating this is a safe, non-destructive operation that can open any URL. The description adds context by specifying it opens 'a new tab' (not just any browser action), which complements the annotations without contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence that states the core functionality without any wasted words. It's front-loaded with the essential action and resource, making it immediately clear what the tool does.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple tool with one optional parameter, good annotations, and no output schema, the description is minimally adequate. However, it lacks context about browser state requirements, what happens if no URL is provided (though the schema covers this), and how it relates to sibling tab management tools.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has 100% description coverage, with the 'url' parameter fully documented in the schema itself. The description doesn't add any parameter information beyond what's in the schema, so it meets the baseline of 3 when schema coverage is high.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Open') and resource ('a new tab'), making the purpose immediately understandable. It doesn't explicitly differentiate from sibling tools like 'browser_tab_list' or 'browser_tab_select', but the verb 'Open' distinguishes it from those listing/selection operations.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools like 'browser_navigate' (which might navigate in current tab) or 'browser_tab_list' (which lists tabs), nor does it specify prerequisites like needing an active browser session.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_tab_selectBRead-only
Select a tab by index
| Name | Required | Description | Default |
|---|---|---|---|
| index | Yes | The index of the tab to select |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, which already convey that this is a safe, non-destructive operation with potential for open-ended outcomes. The description adds minimal context by specifying 'by index', but doesn't elaborate on behavioral aspects like what happens if the index is invalid, whether it changes browser focus, or any side effects. No contradiction with annotations exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence with zero waste—'Select a tab by index'—front-loading the core action. It's appropriately sized for a simple tool, with every word contributing directly to understanding the purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (one parameter, simple operation), annotations covering safety (readOnly, non-destructive), and no output schema, the description is minimally adequate. However, it lacks context on prerequisites (e.g., needing browser_tab_list first) or error handling, leaving gaps for an agent to infer usage correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has 100% description coverage, with the 'index' parameter fully documented as 'The index of the tab to select'. The description 'Select a tab by index' adds no additional meaning beyond this schema, such as index format (e.g., zero-based) or constraints. Baseline 3 is appropriate given high schema coverage.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Select a tab by index' clearly states the verb 'select' and resource 'tab', with the specific mechanism 'by index' distinguishing it from other tab-related tools like browser_tab_list or browser_tab_close. However, it doesn't explicitly differentiate from all sibling tools, as browser_tab_new also involves tabs but for creation rather than selection.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an open browser or existing tabs), when not to use it (e.g., if no tabs exist), or refer to sibling tools like browser_tab_list for listing tabs first. Usage is implied but not explicitly stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_take_screenshotARead-only
Take a screenshot of the current page. You can't perform actions based on the screenshot, use browser_snapshot for actions.
| Name | Required | Description | Default |
|---|---|---|---|
| element | No | Human-readable element description used to obtain permission to screenshot the element. If not provided, the screenshot will be taken of viewport. If element is provided, ref must be provided too. | |
| filename | No | File name to save the screenshot to. Defaults to `page-{timestamp}.{png|jpeg}` if not specified. | |
| raw | No | Whether to return without compression (in PNG format). Default is false, which returns a JPEG image. | |
| ref | No | Exact target element reference from the page snapshot. If not provided, the screenshot will be taken of viewport. If ref is provided, element must be provided too. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, covering the safety profile. The description adds useful context about the tool's limitations (no action capability) and distinguishes it from browser_snapshot, but doesn't provide additional behavioral details like rate limits, authentication needs, or what happens to the screenshot file after creation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise with just two sentences, both of which earn their place by providing essential purpose clarification and usage guidance. No wasted words or redundant information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's moderate complexity (screenshot capture with element targeting options), the description provides good purpose and usage context. With annotations covering safety aspects and no output schema, the main gap is lack of information about return values or what happens to the screenshot file, but the description adequately covers the core functionality.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
With 100% schema description coverage, the input schema already fully documents all 4 parameters. The description doesn't add any parameter-specific information beyond what's in the schema, so it meets the baseline expectation when schema coverage is complete.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the specific action ('Take a screenshot') and resource ('current page'), and explicitly distinguishes it from the sibling tool 'browser_snapshot' by stating 'use browser_snapshot for actions'. This provides clear differentiation from alternatives.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides explicit guidance on when NOT to use this tool ('You can't perform actions based on the screenshot') and names a specific alternative ('use browser_snapshot for actions'). This gives clear context for tool selection versus sibling tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_typeADestructive
Type text into editable element
| Name | Required | Description | Default |
|---|---|---|---|
| element | Yes | Human-readable element description used to obtain permission to interact with the element | |
| ref | Yes | Exact target element reference from the page snapshot | |
| slowly | No | Whether to type one character at a time. Useful for triggering key handlers in the page. By default entire text is filled in at once. | |
| submit | No | Whether to submit entered text (press Enter after) | |
| text | Yes | Text to type into the element |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate readOnlyHint=false, openWorldHint=true, and destructiveHint=true, covering safety and scope. The description adds context by specifying it types into 'editable element,' which clarifies the target beyond annotations. It doesn't contradict annotations, but lacks details on side effects (e.g., triggering events) or error handling, though annotations provide a good baseline.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence ('Type text into editable element') with zero waste. It efficiently conveys the core purpose without unnecessary elaboration, making it highly concise and well-structured for quick understanding.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (interactive browser action with 5 parameters), annotations provide good behavioral context (destructive, open-world), and schema coverage is 100%. However, no output schema exists, and the description lacks details on return values or error cases. It's adequate but has gaps in completeness for a mutation tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with clear parameter descriptions in the schema (e.g., 'element' for permission, 'ref' for target, 'slowly' for character-by-character typing). The description doesn't add meaning beyond the schema, but the schema is comprehensive, so a baseline score of 3 is appropriate as it doesn't compensate or detract.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description 'Type text into editable element' clearly states the action (type) and target (editable element), distinguishing it from siblings like browser_click or browser_press_key. However, it doesn't explicitly differentiate from browser_select_option or browser_file_upload, which also involve input actions, making it clear but not fully sibling-differentiated.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing a page snapshot from browser_snapshot), exclusions (e.g., non-editable elements), or comparisons to siblings like browser_press_key for key presses or browser_select_option for dropdowns.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
browser_wait_forBRead-only
Wait for text to appear or disappear or a specified time to pass
| Name | Required | Description | Default |
|---|---|---|---|
| text | No | The text to wait for | |
| textGone | No | The text to wait for to disappear | |
| time | No | The time to wait in seconds |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true, destructiveHint=false, and openWorldHint=true, covering safety and scope. The description adds minimal behavioral context by specifying what triggers the wait (text appearance/disappearance or time), but doesn't elaborate on timeout behavior, error handling, or interaction with other browser tools. No contradiction with annotations exists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence that front-loads the core functionality. It avoids redundancy and waste, though it could be slightly more structured by separating the text and time conditions for clarity.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's moderate complexity (waiting with multiple triggers), annotations cover safety and scope, and schema fully documents parameters. However, without an output schema, the description doesn't explain return values (e.g., success/failure, timeout errors), leaving gaps in understanding the tool's full behavior in practice.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, fully documenting all three parameters (text, textGone, time). The description mentions these parameters generically ('text to appear or disappear' and 'specified time') but adds no extra semantic details like format examples, mutual exclusivity, or default behaviors, so it meets the baseline without enhancing understanding.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool's purpose as waiting for text to appear/disappear or for time to pass, which is a specific verb+action combination. However, it doesn't explicitly distinguish this from sibling tools like browser_handle_dialog or browser_console_messages that might also involve waiting for specific conditions, though the core functionality is well-defined.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention scenarios where waiting is preferred over other actions (e.g., using browser_handle_dialog for pop-ups) or prerequisites like needing an active browser session, leaving usage context entirely implicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
scan_pageBDestructive
Scan the current page for accessibility violations using Axe
| Name | Required | Description | Default |
|---|---|---|---|
| violationsTag | Yes | Array of tags to filter violations by. If not specified, all violations are returned. |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=false, openWorldHint=true, and destructiveHint=true, indicating this is a non-read-only, open-ended, and potentially destructive operation. The description adds that it scans 'the current page' and uses 'Axe', giving implementation context. However, it doesn't explain what 'destructive' means here (e.g., page reload, state changes) or detail output behavior (e.g., format, timing), leaving gaps despite annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, efficient sentence that front-loads the core purpose without unnecessary words. Every part ('Scan the current page for accessibility violations using Axe') contributes essential information, making it appropriately sized and well-structured for quick understanding.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's moderate complexity (accessibility scanning with filtering), annotations cover safety and scope, and schema fully documents the single parameter. However, without an output schema, the description doesn't explain what the scan returns (e.g., violation details, counts), leaving a gap in understanding results. It's adequate but incomplete for effective use.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, with the parameter 'violationsTag' fully documented in the schema as an array of tags to filter violations. The description adds no parameter-specific information beyond what the schema provides, so it meets the baseline for high schema coverage without compensating value.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the action ('Scan') and resource ('current page') with the specific purpose of finding 'accessibility violations using Axe'. It distinguishes itself from sibling browser tools by focusing on accessibility scanning rather than navigation, interaction, or monitoring. However, it doesn't explicitly differentiate from potential non-existent accessibility siblings.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an open browser page), when scanning is appropriate (e.g., after page load), or what happens if used incorrectly. With many sibling browser tools, this lack of context leaves the agent guessing about proper sequencing.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Tool Schema Changelog
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
25 tool updates
v1.0.0- First observed
browser_click - First observed
browser_close - First observed
browser_console_messages - First observed
browser_drag - First observed
browser_file_upload - First observed
browser_handle_dialog - First observed
browser_hover - First observed
browser_install - First observed
browser_navigate - First observed
browser_navigate_back - First observed
browser_navigate_forward - First observed
browser_network_requests - First observed
browser_pdf_save - First observed
browser_press_key - First observed
browser_resize - First observed
browser_select_option - First observed
browser_snapshot - First observed
browser_tab_close - First observed
browser_tab_list - First observed
browser_tab_new - First observed
browser_tab_select - First observed
browser_take_screenshot - First observed
browser_type - First observed
browser_wait_for - First observed
scan_page
TDQS
Scored across 25 tools
Most tools have distinct purposes, but there is some overlap between browser_snapshot and browser_take_screenshot, as both capture page visuals, though their descriptions clarify different use cases. Other tools like browser_navigate, browser_navigate_back, and browser_navigate_forward are clearly differentiated, and actions like click, hover, and type are well-separated.
All tool names follow a consistent snake_case pattern with a 'browser_' prefix for most tools, except scan_page which still fits the style. The naming is highly predictable, using verb_noun combinations like browser_click, browser_navigate, and browser_tab_list, making it easy to understand and navigate.
With 25 tools, the count is borderline high for an accessibility scanner, as it includes many general browser automation functions beyond core accessibility tasks. While comprehensive, it may feel heavy and could be streamlined by focusing more on accessibility-specific operations rather than broad browser control.
The toolset covers a wide range of browser interactions and includes a dedicated accessibility scanning tool (scan_page), but there are minor gaps such as lacking tools for specific accessibility audits like color contrast checks or ARIA attribute validation. However, the core functionality for navigating, interacting, and scanning pages is well-covered.
Maintenance
Related MCP Connectors
Scan URLs or HTML for WCAG 2.2 violations. 75-rule manifest, weighted score, shareable reports.
Deterministic axe-core accessibility scans (WCAG 2.1 AA, EN 301 549, PDF/UA) via your account.
Scan URLs for WCAG 2.1 violations, generate AI fixes, and produce VPAT 2.5 compliance reports.
Free WCAG 2.2/ADA/508 accessibility MCP: scan, AI fixes, verify, vision audit, localhost tunnel
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