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open-browser-control

open-browser-control

by smankoo
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
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browser_execute_js

Execute JavaScript in a live browser page to extract data, read computed styles, or call page APIs, returning the result directly.

Instructions

Execute JavaScript in the page context and return the result. Useful for extracting specific data, reading computed styles, or interacting with page APIs — often more precise than screenshots for getting exact values.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "expression": "<expression>"
    },
    "name": "browser_execute_js"
  }
}

Input Schema

NameRequiredDescriptionDefault
expressionYesJavaScript expression to evaluate

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.2.0

TDQS

A3.7/5.0
Behavior2/5

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

No annotations exist, so description carries full burden. It mentions 'interact with page APIs' but does not disclose potential side effects (e.g., state modification, CSP restrictions, error behavior). Lacks critical behavioral details for a JS execution tool.

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?

Two sentences, front-loaded with action and result, no wasted words. Efficient and clear.

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

Completeness3/5

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

Covers basic purpose and use cases but omits details on return format, error handling, and async behavior. Adequate but lacks depth for a complex tool.

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 coverage is 100% with parameter 'expression' described. Description adds no extra meaning beyond the schema, earning baseline 3.

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?

Clearly states it executes JavaScript in page context and returns result, with specific use cases (extracting data, reading computed styles, interacting with APIs). Distinguishes from siblings like browser_screenshot and browser_get_dom.

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?

Provides context on when to use (extracting precise data, computed styles) and contrasts with screenshots, but does not explicitly state when not to use.

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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