v8-cpu-profile-decoder-mcp

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analyze_call_tree_path

Find all callers of a specific function in a V8 CPU profile and see how often each invokes it, revealing the code paths that contribute to slowdowns.

Instructions

Finds all callers of a specific function in a V8 CPU profile and returns how often each caller invoked it. Accepts partial, case-insensitive function name matching. Use to answer: what is calling my slow function and how many times?

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": {
      "profile_path": "<profile_path>",
      "function_name": "<function_name>"
    },
    "name": "analyze_call_tree_path"
  }
}

Input Schema

Name	Required	Description
`top_callers`	No	Number of top callers to return (default: 5)
`profile_path`	Yes	Absolute path to the .cpuprofile file
`function_name`	Yes	Function name to search for (partial match, case-insensitive)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Aug 5, 2026

TDQS

A4/5.0

Behavior3/5

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

With no annotations provided, the description carries the burden of behavioral disclosure. It adds value by explaining the matching behavior (partial, case-insensitive) and the return format (caller frequencies), but these are partially redundant with the schema. It does not explicitly state that the tool is read-only or describe behavior for edge cases like no matches, leaving some ambiguity.

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 three sentences, front-loaded with the primary action, and contains no filler. Each sentence contributes meaning: what it does, how matching works, and a concrete use case.

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

Completeness4/5

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

Given the tool's moderate complexity (3 parameters, no output schema), the description adequately covers the core purpose, matching behavior, and output relevance. It could be slightly stronger by noting what happens when no callers are found or emphasizing that it is a read-only operation, but these are minor gaps.

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 each parameter is already well-documented. The description adds minimal extra meaning beyond the schema, mainly clarifying the purpose of the function_name and the nature of the returned data. This aligns with the baseline score of 3 for high schema coverage.

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 the action ('Finds all callers'), the target ('a specific function in a V8 CPU profile'), and the output ('returns how often each caller invoked it'). It distinctly separates this tool from siblings like 'extract_hottest_functions' or 'analyze_gc_pressure' by focusing specifically on caller analysis for a named function.

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?

It provides explicit context with 'Use to answer: what is calling my slow function and how many times?', which tells the agent when to invoke it. However, it does not mention when not to use it or compare it to alternatives, though the sibling tool list offers some degree of differentiation.

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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