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VitexSoftware

mcp-server-webdriver

browser_open

Open a URL in Firefox with optional headless mode, mobile viewport emulation, and automatic capture of JavaScript errors, console output, and network requests via WebDriver BiDi.

Instructions

Open URL in Firefox. Starts a new browser session if none is running.

With enable_bidi=True (default) the session automatically captures: • All JavaScript exceptions (file, line, column, stack trace) • All console.* output (log / warn / error / info / debug) • All network requests with status codes and durations

To test responsive / mobile layouts pass width + height (and optionally user_agent): width=390 height=844 — iPhone 14 width=375 height=667 — iPhone SE width=360 height=800 — Samsung Galaxy S21 width=768 height=1024 — iPad width=1280 height=800 — laptop

geckodriver sources (priority order):

  1. GECKODRIVER_PATH env → 2. apt install gecko-driver → 3. webdriver-manager

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlNoURL to open (default: about:blank)about:blank
widthNoViewport width in pixels. 0 = browser default. E.g. 390 for iPhone 14.
heightNoViewport height in pixels. 0 = browser default. E.g. 844 for iPhone 14.
headlessNoHeadless mode (no visible window)
user_agentNoOverride the browser User-Agent string. Useful for mobile emulation so sites that sniff the UA serve their mobile layout. E.g. 'Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1'
enable_bidiNoEnable WebDriver BiDi for DevTools capture (JS errors, console, network). Requires Firefox + geckodriver ≥ 0.34. Default True.
firefox_binaryNoOptional path to a custom Firefox binary
geckodriver_logNoOptional file path for geckodriver log

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description discloses key behavioral traits beyond annotations: session management, BiDi capture details (JavaScript exceptions, console output, network requests), and responsive mode. It adds significant context that the readOnlyHint=false annotation alone does not convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured with three concise paragraphs: session and BiDi info, responsive testing examples, and geckodriver setup. It is front-loaded with the most critical information and contains no wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (8 parameters, output schema, many siblings), the description covers all necessary aspects: session lifecycle, parameter usage with examples, setup dependencies, and expected outputs (BiDi captures). It is fully adequate for an agent to use correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 100% schema coverage, the description adds substantial value by providing practical examples (viewport sizes for common devices), explaining the purpose of user_agent for mobile emulation, and detailing geckodriver sourcing logic not present in the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Open URL in Firefox' and specifies it starts a new browser session. It distinguishes itself from sibling tools (e.g., browser_navigate, devtools_*) by detailing its session-initialization behavior and BiDi capture capabilities.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit examples for responsive layout testing with width/height values and mentions geckodriver sourcing priority. It implies not to use for existing sessions (use browser_navigate instead), but does not explicitly state when to avoid this tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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