Chrome Course MCP

by CrispyW0nton

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JavaScript

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chrome_launch

Launch Chrome with DevTools Protocol enabled for automated inspection, or open a new tab if Chrome is already running.

Instructions

Launch a Chrome window with the DevTools Protocol enabled, or open a new tab if it is already running.

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": "chrome_launch"
  }
}

Input Schema

Name	Required	Default
`url`	No	about:blank
`waitMs`	No
`debugUrl`	No	http://127.0.0.1:9222
`extraArgs`	No
`chromePath`	No
`userDataDir`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 2, 2026

TDQS

B3.4/5.0

Behavior3/5

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

With no annotations provided, the description carries the transparency burden. It discloses key behaviors: enabling DevTools Protocol and conditionally opening a new tab if Chrome is already running. However, it omits side effects, prerequisites, or failure modes such as port conflicts or behavior when extraArgs are used. The provided details are useful but minimal.

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, direct sentence that front-loads the main action. It contains no filler or redundant information, making it highly concise and appropriately structured for its length.

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

Completeness2/5

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

The tool is complex with 6 parameters and no output schema, but the description only covers the basic launch/tab behavior. It does not explain return values, how to use the tool with respect to siblings, or edge cases like merging with an existing session. The description is too minimal for the tool's complexity, especially without annotations or schema descriptions.

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

Parameters2/5

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

The schema has 6 optional parameters with zero description coverage, and the description does not explain any of them (e.g., debugUrl, waitMs, extraArgs). Although the context hints at debugUrl via DevTools Protocol, the description fails to compensate for the lack of parameter documentation, leaving most parameters underspecified.

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

Purpose4/5

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

The description clearly identifies the tool's action: launching a Chrome window with DevTools Protocol enabled, or opening a new tab if already running. This is a specific verb+resource pair, but it does not explicitly distinguish from the sibling tool chrome_open_tab, which also opens tabs, creating some ambiguity.

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 clear context for when to use the tool: when you need a Chrome window with debugging enabled or want to open a tab in a running instance. However, it does not mention alternatives or when not to use it, especially given the existence of chrome_open_tab for tab opening.

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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