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Fast Browser MCP

Fast Browser MCP

by kqlio67
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

browser_start_coverage

Start precise V8 code coverage measurement across subsequent browser interactions to track block-level coverage and function execution counts.

Instructions

Start precise V8 code coverage measurement across subsequent browser interactions.

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": "browser_start_coverage"
  }
}

Input Schema

NameRequiredDescriptionDefault
detailedNoCollect block-level precise coverage
call_countNoCount function executions

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv0.12.0

TDQS

A3.5/5.0
Behavior3/5

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

With no annotations, the description carries the full burden. It usefully discloses the stateful, forward-looking nature of the tool ('subsequent browser interactions'), but says nothing about performance overhead, whether collection can be started twice, or that session state persists until stopped.

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?

A single front-loaded sentence with no filler; the verb and scope appear immediately and every word earns its place.

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?

For a simple two-parameter tool with a full schema and no output schema, the description is minimally adequate. However, it omits the lifecycle context – that results are retrieved later via browser_observe_coverage/browser_stop_coverage – which an agent needs to use it correctly in sequence.

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% – both 'detailed' (block-level precise coverage) and 'call_count' (count function executions) are documented in the schema. The description adds no meaning beyond that, so the baseline 3 applies.

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?

States a specific verb and resource: 'Start precise V8 code coverage measurement', plus the scope 'across subsequent browser interactions'. It does not name the sibling tools (browser_stop_coverage, browser_observe_coverage) that complete the workflow, so sibling differentiation is only implicit via the word 'Start'.

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

Usage Guidelines3/5

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

Usage is only implied: 'across subsequent browser interactions' hints that this must precede the interactions to be measured, but the description never states when to use it versus browser_observe_coverage or that browser_stop_coverage must be called to end collection. No exclusions or alternatives are given.

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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