Bridge STDIO Clients to HTTP MCP Servers

mcp-stdio-to-streamable-http-adapter MCP Server

Integrate any MCP Client that has STDIO MCP Server Support (most do) with the Streamable HTTP MCP Servers

If you have a Streamable HTTP MCP Server, forking this, hardcoding the URI and publishing will give you a repo that you can point to, add to directories and let people use via STDIO.

Note: This has similarities to the mcp-remote package

Why?

The MCP Spec to add a Streamable HTTP Transport landed end of March 2025 and as of the end of April, no clients have adopted support. The typescript-sdk has merged the code, but not released. The Python SDK is still in development to support it. The Inspector supports it, but that's it.

This leaves developers in an awkward position. Develop the MCP Server using STDIO or SSE (deprecated) so it works with clients or develop with Streamable HTTP transport, but nobody can use it.

I (ferrants) want to start integrating the Streamable HTTP MCP Servers beyond just the inspector, so I need a way to connect them to clients and LLMs right away!

This package aims to bridge the cap by being a STDIO MCP Server that relays to your Streamable HTTP MCP Server. This makes all MCP Clients support Streamable HTTP right away. And now developers can develop the Streamable HTTP MCP Servers and provide an installation method.

Installation

To add OpenAI to Claude Desktop, add the server config:

On MacOS: ~/Library/Application Support/Claude/claude_desktop_config.json

On Windows: %APPDATA%/Claude/claude_desktop_config.json

Env Vars

• URI: The URL of the Streamable HTTP MCP Server. This is required.
• MCP_NAME: The name of the MCP Server. This is optional. If you configure multiple, this is required so they do not have the same names.
• BEARER_TOKEN: The Bearer token for the Streamable HTTP MCP Server. This is optional. If specified, this will be sent along in the Authorization header.

Configuration

You can use it via npx in your Claude Desktop configuration like this:

{
  "mcpServers": {
    "my-saas-app-development": {
      "command": "npx",
      "args": [
        "@pyroprompts/mcp-stdio-to-streamable-http-adapter"
      ],
      "env": {
        "URI": "http://localhost:3002/mcp",
        "MCP_NAME": "local-custom-streamable-http-adapter"
      }
    }
  }
}

Or, if you clone the repo, you can build and use in your Claude Desktop configuration like this:

{
  "mcpServers": {
    "my-saas-app-development": {
      "command": "node",
      "args": [
        "/path/to/mcp-stdio-to-streamable-http-adapter/build/index.js"
      ],
      "env": {
        "URI": "http://localhost:3002/mcp",
        "MCP_NAME": "local-custom-streamable-http-adapter"
      }
    }
  }
}

You can add multiple providers by referencing the same MCP server multiple times, but with different env arguments:

{
  "mcpServers": {
    "my-saas-app-development": {
      "command": "node",
      "args": [
        "/path/to/mcp-stdio-to-streamable-http-adapter/build/index.js"
      ],
      "env": {
        "URI": "http://localhost:3002/mcp",
        "MCP_NAME": "local-custom-streamable-http-adapter"
      }
    },
    "pyroprompts": {
      "command": "node",
      "args": [
        "/path/to/mcp-stdio-to-streamable-http-adapter/build/index.js"
      ],
      "env": {
        "URI": "https://api.pyroprompts.com/mcp",
        "MCP_NAME": "pyroprompts",
        "BEARER_TOKEN": "abcdefg"
      }
    }
  }
}

With these three, you'll see a tool for each in the Claude Desktop Home:

And then you can chat with other LLMs and it shows in chat like this:

Or, configure in LibreChat like:

  my-saas-app-development:
    type: stdio
    command: npx
    args:
      - -y
      - @pyroprompts/mcp-stdio-to-streamable-http-adapter
    env:
      URI: "http://localhost:3002/mcp",
      MCP_NAME: "my-custom-saas-app"
      PATH: '/usr/local/bin:/usr/bin:/bin'

And it shows in LibreChat:

Development

Install dependencies:

npm install

Build the server:

npm run build

For development with auto-rebuild:

npm run watch

Debugging

Since MCP servers communicate over stdio, debugging can be challenging. We recommend using the MCP Inspector, which is available as a package script:

npm run inspector

The Inspector will provide a URL to access debugging tools in your browser.