mitmproxy-mcp

HTTP/HTTPS traffic analysis, interception, and replay through mitmproxy.

Prerequisites

• mitmproxy running with the mitmproxy-mcp addon loaded
• MCP server available at http://localhost:9011/sse (SSE transport)

If the MCP server is not connected, tell the user to start mitmproxy first:

mitmproxy      # or mitmweb, or mitmdump

The addon and MCP server start automatically if configured in ~/.mitmproxy/config.yaml.
For dependency-safe startup, install shims once with mitmproxy-mcp install-shims --force.

When to Use This Skill

• User asks to inspect, debug, or analyze HTTP traffic
• User wants to replay or modify an HTTP request
• User wants to intercept requests matching a pattern
• User needs to export captured traffic (HAR format)
• User is doing API debugging or security testing

Available Tools (20)

Flow Tools -- querying captured traffic

• get_flows -- list captured flows with optional filtering by method, URL pattern, or status code. Supports limit and offset for pagination.
• get_flow_by_id -- get full request and response details for a single flow
• search_flows -- search flows by regex pattern across URL, method, status, and headers
• get_flow_request -- get only the request portion of a flow
• get_flow_response -- get only the response portion of a flow
• get_flow_count -- count of currently stored flows
• clear_flows -- clear all stored flows and clear mitmproxy's flow view when sync includes clear
• export_flows -- export flows to HAR 1.2 format. Optionally pass specific flow IDs.

Replay Tools -- sending and modifying requests

• replay_request -- replay a captured request exactly as-is. Replays in-place when view sync includes replay; otherwise creates a detached replay flow.
• send_request -- send a new HTTP request. Parameters: url (required), method (default GET), headers, body.
• modify_and_send -- take an existing flow, change its method/url/headers/body, and send it. Useful for testing variations.
• duplicate_flow -- clone a flow without sending it. Useful for before/after comparisons.

Replay tool flows are reflected to mitmproxy's flow list when mcp_view_sync_actions includes replay (default: all).

Intercept Tools -- pausing and controlling live traffic

• set_intercept_filter -- set a mitmproxy filter expression to intercept matching requests. Uses mitmproxy filter syntax: ~u example.com, ~m POST, ~u api & ~m GET. Pass empty string to disable.
• get_intercepted_flows -- list flows currently paused by interception
• resume_flow -- resume a single intercepted flow
• resume_all -- resume all intercepted flows
• drop_flow -- drop/kill an intercepted flow without forwarding it

Config Tools -- proxy settings

• get_options -- get current mitmproxy option values. Pass specific keys or get curated defaults.
• set_option -- set a mitmproxy option at runtime. Some dangerous options (listen_host, listen_port, mode, server, ssl_insecure) are blocked.
• get_status -- get proxy status: version, listen address, mode, flow count, intercept settings.

Workflow Patterns

Basic traffic inspection

1. Make sure mitmproxy is running and proxying the target traffic
2. Use get_flows to see what has been captured
3. Use get_flow_by_id to drill into specific requests/responses
4. Use search_flows with a regex to find specific patterns

Replaying and modifying requests

1. Find the flow you want with get_flows or search_flows
2. Use replay_request to resend it exactly
3. Or use modify_and_send to change headers, body, or URL before sending
4. Compare the original and modified responses

Intercepting live traffic

1. Set a filter with set_intercept_filter (e.g. ~u api.example.com & ~m POST)
2. Wait for matching requests -- they will be paused
3. Use get_intercepted_flows to see what is waiting
4. Use resume_flow or drop_flow to control each one
5. Use set_intercept_filter with empty string to stop intercepting

Important Notes

• Sensitive data redaction is off by default. Enable with mcp_redact: true in mitmproxy config to redact tokens, passwords, API keys, and JWTs
• Use mcp_view_sync_actions to control what syncs to mitmproxy's view (all, none, replay, clear, or replay,clear)
• Request/response bodies are truncated to 10KB to prevent context overflow
• All data is in-memory only -- cleared when mitmproxy stops
• The proxy stores up to 1000 flows by default (oldest evicted first)