openapi2mcp

What is openapi2mcp?

openapi2mcp is a command-line tool that converts OpenAPI 3.x specification files into ready-to-run FastMCP servers. It is designed for developers who want to quickly expose existing REST APIs as MCP (Model Context Protocol) servers using standard transports.

How to use openapi2mcp?

Install via poetry install. Then use the openapi2mcp generate command to create a Python MCP server from a JSON or YAML OpenAPI spec, specifying input, output, transport (stdio or google_pubsub), an optional resource mount path, and an optional llms.txt file. Validate the generated code with openapi2mcp check and display the version with openapi2mcp version.

Key features of openapi2mcp

• Generates FastMCP server code from OpenAPI 3.x specs.
• Supports stdio and Google Pub/Sub transports.
• Mount path customization for server resources.
• Automatic generation of llms.txt for LLM tool descriptions.
• Built-in code validation with the check command.
• Simple CLI with three commands: generate, check, version.

Use cases of openapi2mcp

• Convert an existing REST API (OpenAPI spec) into an MCP server.
• Rapidly prototype an MCP server for LLM tool integration.
• Generate an llms.txt file to document MCP tools for language models.
• Validate generated MCP server code before deployment.

FAQ from openapi2mcp

How do I install openapi2mcp?

Run poetry install in the project directory. A specific installation method is not detailed beyond this.

What transport options are available?

The generate command accepts --transport with values stdio or google_pubsub. The default is stdio.

How can I check a generated server file for errors?

Use openapi2mcp check --server-file <path> to verify syntax and key MCP patterns in the generated Python file.