OpenMCP

OpenMCP is a dual-purpose framework: a standard for converting web APIs into MCP servers and an open-source registry of servers that follow that standard. Each OpenMCP server exposes a token-efficient MCP interface that enables MCP clients to make requests to a target web API on behalf of users. Together, the servers in the registry enable client LLMs to fetch data and perform actions across a broad set of domains, providing a scalable, interoperable way to integrate external services with MCP clients. The documentation guides you through creating a server, adding it to MCP clients, and converting various web API formats into OpenMCP-compatible servers, covering REST, gRPC, JSON-RPC, GraphQL, SOAP, and PostgREST variants.

OpenMCP enables developers to expose any web API as an MCP server and register it for MCP clients to consume. This streamlines how large language models (LLMs) interact with external services, offering a token-efficient interface and a single compliance model for diverse APIs. Typical use cases include configuring a server for your API, adding it to an MCP client, and converting an existing web API into an OpenMCP-compliant server. The docs provide practical examples for integrating with clients via the CLI configuration flow (Claude Desktop, Cursor, and other clients) and outline the supported formats for conversion (REST, gRPC, JSON-RPC, GraphQL, SOAP, PostgREST). Example configuration snippets from the documentation are shown below to illustrate how to wire OpenMCP servers into your client projects:

Claude Desktop example:
npx @open-mcp/config add {server-id} \
~/Library/Application/ Claude/claude_desktop_config.json \
--ENV_VAR=abc123

Cursor example:
npx @open-mcp/config add {server-id} \
.cursor/mcp.json \
--ENV_VAR=abc123

Other clients example:
npx @open-mcp/config add {server-id} \
/path/to/config.json \
--ENV_VAR=abc123