echo-mcp

A tiny MCP server for testing clients and transport setup. It exposes one tool, echo, which returns the input message unchanged and also prints it to stderr.

Built with rmcp.

Installation

Cargo

echo-mcp is published on crates.io, so you can install the latest stable build with:

cargo install --locked echo-mcp

If you already have echo-mcp installed, rerun the command with --force to upgrade.

GitHub releases

Download a pre-built binary from the release page

Release assets are machine-specific, so pick the archive that matches your OS once the download page opens.

Features

• stdio transport for local MCP client integrations
• streamable HTTP transport on /mcp
• a single echo tool that accepts:

{
  "message": "hello"
}

and returns:

hello

The same message is also written to stderr when the tool receives it.

Run

echo-mcp stdio

echo-mcp http --bind 127.0.0.1:8000

The streamable HTTP endpoint will be available at http://127.0.0.1:8000/mcp.

Tool

• echo Returns the provided message exactly as received, and writes it to stderr.

Example MCP Client Config

{
  "mcpServers": {
    "echo-mcp": {
      "command": "echo-mcp",
      "args": ["stdio"]
    }
  }
}