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Chrome Browser Control

Chrome Browser Control

by vKongv
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TypeScript
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Activate Chrome tab

activate_tab

Focus a specified Chrome tab and its window to resolve DOCUMENT_HIDDEN errors when click or type actions fail. Waits for the tab to become visible, then returns its visibility state; use allowHidden only when the tab is already hidden.

Instructions

Focus an allowed tab and its window without navigating. Waits until the document reports visibilityState visible or a short timeout elapses. Returns visibilityState and visible; reason is present only when visible is false. focused is not success. Use this when click/type fail with DOCUMENT_HIDDEN. Pass allowHidden=true only when visibilityState is hidden. If reason is host_permission_denied or document_unavailable, grant permission or reload; allowHidden will not help. Does not change the page URL.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "activate_tab"
  }
}

Input Schema

NameRequiredDescriptionDefault
tabIdNoOptional Chrome tab id. Defaults to the claimed session tab, then the active tab.
sessionTabIdNoOptional claimed tab session id returned by claim_tab.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.4.0

TDQS

A4.7/5.0
Behavior5/5

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

With no annotations provided, the description carries the full burden and does so thoroughly. It discloses the waiting behavior (timeout), the return fields (visibilityState, visible, reason), the fact that 'focused is not success', and that it does not change the URL. It also covers permission-denied and document-unavailable scenarios.

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 a single, well-structured paragraph that front-loads the core purpose, then covers conditions, usage, and caveats. Every sentence adds value and there is no redundancy. It is concise while being comprehensive.

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?

Despite no output schema and no annotations, the description covers the essential behavior, return values, error reasoning, and usage constraints. It leaves no critical gap for an agent to call the tool correctly, given the tool's moderate complexity.

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

Parameters3/5

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

Schema description coverage is 100%, so both parameters (tabId and sessionTabId) are already documented in the schema, including the default resolution order. The description does not add parameter-specific detail beyond the schema, so a baseline of 3 is appropriate.

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 states a specific verb ('Focus') and resource ('an allowed tab and its window') and explicitly distinguishes from navigation ('without navigating'). It also mentions the context of failure (DOCUMENT_HIDDEN), making it clear what the tool does and how it differs from siblings like navigate.

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

Usage Guidelines5/5

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

The description provides explicit when-to-use guidance ('Use this when click/type fail with DOCUMENT_HIDDEN') and when-not-to-use allowHidden ('Pass allowHidden=true only when visibilityState is hidden'), plus troubleshooting for specific reason codes. It clearly tells the agent when to choose this tool over alternatives.

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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