mitmproxy-mcp

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proxy_start

Start an HTTP capture proxy to intercept and inspect network traffic. Configure host, port, filters, SSL handling, and optional upstream proxy.

Instructions

Start the mitmproxy capture proxy.

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": "proxy_start"
  }
}

Input Schema

Name	Required	Default
`host`	No	127.0.0.1
`port`	No
`capture_filter`	No
`ssl_insecure`	No
`upstream_proxy`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jun 18, 2026

TDQS

C2.1/5.0

Behavior1/5

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

No annotations, and the description fails to disclose behavioral traits such as blocking behavior, side effects, permissions, error states, or impact on existing proxy instances.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness2/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Extremely short single sentence, but it is under-specification rather than concise. It does not efficiently convey important details.

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

Completeness1/5

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

The description is insufficient given five parameters, no annotations, and an output schema. It fails to explain return values, configuration, or usage context.

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

Parameters1/5

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

Schema description coverage is 0%, and the tool description provides no explanation of the 5 parameters (host, port, capture_filter, etc.). The schema only gives defaults and types.

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 states 'Start the mitmproxy capture proxy,' which is a specific verb+resource. It distinguishes from siblings like proxy_status and proxy_stop. However, it lacks details about mitmproxy's role.

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus alternatives like proxy_stop or flow tools. No prerequisites or exclusions are mentioned.

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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