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debug-mcp-server

by silentwasd
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debug-mcp-server

A minimal Model Context Protocol server for debugging MCP clients. It echoes back everything it receives — tool arguments, session IDs, metadata — so you can inspect exactly what your client is sending.

Uses Streamable HTTP transport (no stdio).

Tools

Tool

Description

debug_echo

Returns all passed arguments as JSON along with sessionId and _meta

debug_inspect

Recursively prints the type and structure of any value

debug_server_info

Returns Node.js version, platform, uptime, memory usage

Related MCP server: Echo MCP Server

Requirements

  • Node.js 18+

Installation

git clone https://github.com/your-username/debug-mcp-server.git
cd debug-mcp-server
npm install

Usage

npm start
# Server listening on http://127.0.0.1:3000/mcp

Environment variables:

Variable

Default

Description

PORT

3000

Port to listen on

HOST

127.0.0.1

Host to bind to

Connect to Claude Code

claude mcp add --transport http debug-mcp-server http://127.0.0.1:3000/mcp

API

All requests go to POST /mcp. The session lifecycle follows the MCP Streamable HTTP spec:

  1. Initialize — send an initialize request without mcp-session-id; the server responds with the header mcp-session-id

  2. Subsequent requests — include mcp-session-id in every request

  3. SSE stream — GET /mcp with mcp-session-id opens a server-sent events stream for server→client notifications

  4. Terminate — DELETE /mcp with mcp-session-id closes the session

Every incoming request (headers + body) is logged to stdout.

Example session

# 1. Initialize
curl -sD - -X POST http://127.0.0.1:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{
    "jsonrpc": "2.0", "id": 1, "method": "initialize",
    "params": {
      "protocolVersion": "2024-11-05",
      "capabilities": {},
      "clientInfo": { "name": "test", "version": "1.0" }
    }
  }'
# → header: mcp-session-id: <SESSION_ID>

# 2. Call debug_echo
curl -s -X POST http://127.0.0.1:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "mcp-session-id: <SESSION_ID>" \
  -d '{
    "jsonrpc": "2.0", "id": 2, "method": "tools/call",
    "params": {
      "name": "debug_echo",
      "arguments": { "message": "hello", "number": 42, "flag": true }
    }
  }'

Response from debug_echo:

{
  "tool": "debug_echo",
  "timestamp": "2026-06-23T10:56:52.842Z",
  "params": {
    "message": "hello",
    "number": 42,
    "flag": true
  },
  "meta": null,
  "sessionId": "<SESSION_ID>"
}

License

MIT

This server cannot be deployed

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Maintenance

ActivityStale
ResponsivenessNo issues

Resources

Related MCP Connectors

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