MCP Composer

MCP Composer is a FastMCP server that mounts other MCP servers and exposes their tools through one endpoint. Register servers at runtime with JSON. Supported member types are HTTP, stdio, OpenAPI, and GraphQL.

Install

Python 3.11, 3.12, or 3.13 and uv.

git clone https://github.com/ibm/mcp-composer.git
cd mcp-composer/modules/mcp_composer
uv sync --group dev

The package is mcp-composer. There is no separate application package.

Run

mcp-composer --mode http --host 127.0.0.1 --port 9000

HTTP binds to loopback unless you configure authentication. A non-loopback bind without auth is rejected. Stdio member servers run only when the resolved command is listed in MCP_COMPOSER_STDIO_ALLOWLIST.

Point the composer at a member list:

mcp-composer --mode http --host 127.0.0.1 --port 9000 \
  --config_path example/member_servers.json

A fuller sample is example/unified_config.json. Guides are in docs/guide.

Domain composers

These processes start one tool surface and still mount member servers from the usual config. They bind 127.0.0.1.

cd modules/mcp_composer
uv run composers/think_composer.py
uv run composers/catalog_composer.py

Think Composer (think-composer) exposes sequential_thinking. Catalog Composer mounts the skill, agent, and workflow catalogs. See Think Composer and Catalog Composer.

Project

License	Apache 2.0
Contributing	CONTRIBUTING.md
Security	SECURITY.md
Code of conduct	CODE_OF_CONDUCT.md
Changelog	CHANGELOG.md

Report vulnerabilities privately. See SECURITY.md.