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MCP-Bridge

by SecretiveShell · SecretiveShell/MCP-Bridge

Use MCP tools from any OpenAI-compatible client — LibreChat, Open WebUI, your custom app — without native MCP support. Middleware that translates.

MCP-Bridge sits between your OpenAI-compatible client and inference backend. It advertises MCP server tools as OpenAI function-calling tools, dispatches calls, and returns results to complete the loop. Useful when your favorite chat UI doesn't speak MCP but speaks OpenAI.

Why use it

Key features

Live Demo

What it looks like in practice

bridge.replay ▶ ready
0/0

Install

Pick your client

~/Library/Application Support/Claude/claude_desktop_config.json  · Windows: %APPDATA%\Claude\claude_desktop_config.json
{
  "mcpServers": {
    "bridge": {
      "command": "uvx",
      "args": [
        "MCP-Bridge"
      ],
      "_inferred": true
    }
  }
}

Open Claude Desktop → Settings → Developer → Edit Config. Restart after saving.

~/.cursor/mcp.json · .cursor/mcp.json
{
  "mcpServers": {
    "bridge": {
      "command": "uvx",
      "args": [
        "MCP-Bridge"
      ],
      "_inferred": true
    }
  }
}

Cursor uses the same mcpServers schema as Claude Desktop. Project config wins over global.

VS Code → Cline → MCP Servers → Edit
{
  "mcpServers": {
    "bridge": {
      "command": "uvx",
      "args": [
        "MCP-Bridge"
      ],
      "_inferred": true
    }
  }
}

Click the MCP Servers icon in the Cline sidebar, then "Edit Configuration".

~/.codeium/windsurf/mcp_config.json
{
  "mcpServers": {
    "bridge": {
      "command": "uvx",
      "args": [
        "MCP-Bridge"
      ],
      "_inferred": true
    }
  }
}

Same shape as Claude Desktop. Restart Windsurf to pick up changes.

~/.continue/config.json
{
  "mcpServers": [
    {
      "name": "bridge",
      "command": "uvx",
      "args": [
        "MCP-Bridge"
      ]
    }
  ]
}

Continue uses an array of server objects rather than a map.

~/.config/zed/settings.json
{
  "context_servers": {
    "bridge": {
      "command": {
        "path": "uvx",
        "args": [
          "MCP-Bridge"
        ]
      }
    }
  }
}

Add to context_servers. Zed hot-reloads on save.

claude mcp add bridge -- uvx MCP-Bridge

One-liner. Verify with claude mcp list. Remove with claude mcp remove.

Use Cases

Real-world ways to use MCP-Bridge

Add MCP tools to LibreChat / any OpenAI-compatible chat UI

👤 Self-hosters of OSS chat frontends ⏱ ~30 min intermediate

When to use: You're running LibreChat, Big-AGI, or a custom app that calls /v1/chat/completions and wants tool use, but it doesn't speak MCP.

Prerequisites
  • An OpenAI-compatible inference backend — OpenAI, Anthropic-via-proxy, vLLM, Ollama, etc.
  • At least one MCP server you want to expose — filesystem, fetch, postgres — whatever you've got
Flow
  1. Write config.json
    Write me an MCP-Bridge config.json that proxies OpenAI and exposes filesystem MCP (rooted at /data) and fetch MCP.✓ Copied
    → Valid config with inference_server and mcp_servers sections
  2. Run via Docker
    Give me the docker run command to start MCP-Bridge using this config on port 8000.✓ Copied
    → Working docker command with volume mounts
  3. Point the chat UI at the bridge
    Show me what API base URL to set in LibreChat to use the bridge instead of OpenAI directly.✓ Copied
    → Config pointing to http://localhost:8000/v1

Outcome: LibreChat conversations can now call filesystem and fetch tools, transparently.

Pitfalls
  • Not all OpenAI-compatible clients support tool calls — Verify your UI supports functions in responses before wiring; check its docs for 'tool calling' support
  • Streaming responses not yet implemented — Disable streaming in the client; use non-streaming endpoints
Combine with: filesystem · fetch

Give your own Python/JS agent framework MCP tool access

👤 Devs building custom agents on OpenAI SDK ⏱ ~25 min intermediate

When to use: You're building with the raw OpenAI SDK (or LangChain's OpenAI client) and want to plug in the MCP ecosystem without rewriting the agent.

Flow
  1. Start MCP-Bridge locally
    Run MCP-Bridge with upstream set to OpenAI and these MCP servers: [list].✓ Copied
    → Bridge listening on :8000
  2. Point OpenAI client base_url at the bridge
    Show me Python SDK init: client = OpenAI(base_url='http://localhost:8000/v1', api_key=...). Then call chat completions.✓ Copied
    → Code snippet that works unchanged

Outcome: Zero-touch tool access for your existing agent code.

Pitfalls
  • Bridge is a single point of failure — For prod, run with supervisord/systemd and healthcheck endpoint

Combinations

Pair with other MCPs for X10 leverage

bridge + filesystem + fetch

Budget self-hosted ChatGPT replacement with real tool use

Expose filesystem (rooted at ~/Notes) and fetch via MCP-Bridge, then use LibreChat to browse + summarize.✓ Copied

Tools

What this MCP exposes

ToolInputsWhen to callCost
POST /v1/chat/completions OpenAI-compatible messages + tools omitted (auto-injected) Main entrypoint — drop-in for OpenAI 1 LLM call + N tool calls
GET /tools Discover what's available free
SSE /bridge Attach an external MCP client to the bridge over SSE free

Cost & Limits

What this costs to run

API quota
Pass-through — whatever your upstream inference provider charges
Tokens per call
Bridge adds ~100-500 tokens of tool definitions per request
Monetary
Free (MIT). You pay for your LLM + wherever you host it.
Tip
Only attach MCP servers you need — every attached tool bloats the system prompt.

Security

Permissions, secrets, blast radius

Credential storage: Upstream API key + MCP server creds in config.json; lock down file permissions
Data egress: Requests go to your configured upstream (e.g. OpenAI) + whichever MCP servers
Never grant: Expose the bridge to the internet without enabling bearer auth

Troubleshooting

Common errors and fixes

Client says 'tool_use not supported'

Upstream model or client UI doesn't support function calling. Use a model that does (gpt-4o, claude, llama 3.1+).

MCP server connection refused

Check the command in config.json actually runs. Bridge runs it as subprocess; test manually: npx -y the-mcp.

401 from bridge when auth enabled

Set Authorization: Bearer <key> header; the key must be in config under security.auth.keys.

Alternatives

MCP-Bridge vs others

AlternativeWhen to use it insteadTradeoff
Open WebUI native MCPYou specifically use Open WebUI 0.6.31+Built-in — no bridge needed, but Open WebUI only
LiteLLM with custom callbacksYou want multi-provider routing + tool injectionMore complex; LiteLLM doesn't natively speak MCP either
mcpoYou want to expose MCP tools as plain OpenAPI for non-LLM clients tooDifferent shape — OpenAPI-first rather than chat-completions-first

More

Resources

📖 Read the official README on GitHub

🐙 Browse open issues

🔍 Browse all 400+ MCP servers and Skills