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mitmweb-mcp

mitmweb-mcp

by numb747
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

replay_flow

Replay a request with modified method, headers, or body, and view the response as a new flow in mitmweb UI. Existing flows remain unchanged.

Instructions

Replay a request, optionally rewriting method, headers or body (like Burp Repeater).

The request is sent with curl_cffi using browser TLS fingerprint impersonation, and it goes through your own mitmproxy, so the result appears as a new flow in your mitmweb UI where you can see it. Existing flows are never modified.

headers overrides or adds headers, e.g. {"Authorization": "Bearer NEW"}; omit to reuse the original. body replaces the request body (dicts/lists are serialised to JSON). impersonate accepts chrome / chrome131 / chrome142 / safari / firefox / edge.

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": {
      "flow_id": "<flow_id>"
    },
    "name": "replay_flow"
  }
}

Input Schema

NameRequiredDescriptionDefault
bodyNo
methodNo
flow_idYes
headersNo
timeoutNo
body_maxNo
impersonateNochrome

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4.4/5.0
Behavior4/5

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

With no annotations, the description carries the full burden, and it does well: it discloses that the request goes through mitmproxy with curl_cffi/browser impersonation, that this creates a new flow in mitmweb, and that existing flows are never modified. It could add what happens on timeout or failure, but the key behavioral safety profile is clear.

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?

Three short paragraphs each earn their place: purpose, side-effect/behavior, and parameter semantics. The most important scoping statement ('existing flows are never modified') is placed early, and the example makes the headers semantics concrete without bloat.

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?

The description covers what the tool does, how the request is transported, the side effect in the UI, and how the main optional parameters behave. Given that an output schema exists, return values are not required; minor gaps around body_max/timeout keep this from a 5.

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

Parameters4/5

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

Despite 0% schema description coverage, the description explains the important parameters: header override/add semantics with an example, body replacement with JSON serialization for dicts/lists, and accepted impersonate values. It leaves timeout and body_max to their names/defaults, but the core parameters are meaningfully documented.

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?

States the precise action 'Replay a request' and immediately adds the optional modifications (method, headers, body), so an agent knows exactly what the tool does. The 'like Burp Repeater' analogy and the note that it creates a new flow while existing flows are never modified clearly separate it from the inspection/status/diff sibling tools.

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 gives clear context: it is for replaying a captured request, optionally rewriting it, and observing the result as a new flow in mitmweb. It does not explicitly compare itself to sibling tools like inspect_flow or generate_code, so it stops short of a 5.

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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