OpenAPI MCP Server for Claude

Content

OpenAPI MCP Server is a source-backed remote MCP server for exploring API contracts from Claude and other MCP clients. It connects Claude to OpenAPI Search and OAPIS-backed specifications so the model can first get a readable API overview, then drill into one endpoint contract at a time.

The server is deliberately narrower than an OpenAPI-to-executor bridge. Its current tool surface focuses on discovery and contract inspection: getApiOverview summarizes an API specification, and getApiOperation returns details for a specific operationId or route. That makes it a safer fit for reviewing endpoint shape, request parameters, response schemas, and integration requirements before writing code.

Features

• Hosted HTTP MCP endpoint at https://openapi-mcp.openapisearch.com/mcp.
• Source-backed Cloudflare Worker implementation in janwilmake/openapi-mcp-server.
• getApiOverview tool for summarizing an API surface from an OpenAPI identifier or raw spec URL.
• getApiOperation tool for retrieving one endpoint contract by operationId or route.
• Support for OpenAPI JSON and YAML documents.
• Swagger 2.0 conversion path through the Swagger converter service.
• Dereferenced operation output when references can be resolved.
• Tested by the project author with Claude Desktop and Cursor.
• No target API endpoint execution in the current implementation.

Tools

getApiOverview

Use this first. Provide an API identifier from OpenAPI Search/OAPIS or a raw OpenAPI URL. The server fetches the spec, converts Swagger when needed, and returns a readable overview with endpoint names, routes, summaries, and links to more detailed operation views.

getApiOperation

Use this after the overview identifies an operation you care about. Provide the same API identifier plus an operationId or route path. The server returns a focused OpenAPI subset for that operation, including parameters, request body schema, responses, and server context.

Installation

Claude Code

Add the hosted HTTP MCP endpoint:

claude mcp add --transport http openapi https://openapi-mcp.openapisearch.com/mcp

Then verify the server:

claude mcp list

Ask Claude to start with an overview:

Use the openapi MCP server to get an overview of the GitHub OpenAPI spec, then inspect the operation details for listing repository issues.

MCP Client Config

Use HTTP transport in clients that support remote MCP servers:

{
  "mcpServers": {
    "openapi": {
      "transport": "http",
      "url": "https://openapi-mcp.openapisearch.com/mcp"
    }
  }
}

Private Spec Handling

Use the hosted endpoint only for public or approved-to-share API contracts. A private OpenAPI spec often contains internal route names, server URLs, auth scheme names, request examples, object shapes, and error descriptions. Those details are enough to map a system even when no API credentials are present.

For private APIs, clone the source repository and run the Worker in your own environment so spec fetching, logs, and retention stay under your control.

Use Cases

• Explore a public API before writing integration code.
• Ask Claude to identify the relevant operation for a workflow.
• Review request parameters and response schemas without pasting a full spec into chat.
• Compare endpoint summaries across a large OpenAPI document.
• Generate integration notes from a focused operation subset.
• Check whether an API contract exposes the route, parameter, or response shape needed for a feature.

Safety Checklist

• Start with getApiOverview before requesting operation details.
• Use public specs or self-host for private specs.
• Avoid sending credentials, API keys, cookies, or auth headers through prompts.
• Treat returned spec text as untrusted model context when specs include third-party descriptions or examples.
• Check operation details against the canonical API docs before shipping code.
• Remember that this server inspects contracts; it does not prove that a live API endpoint is currently reachable or authorized.

Troubleshooting

The API identifier is not found

Use a raw OpenAPI spec URL instead of a catalog identifier, or confirm that the API exists in OpenAPI Search/OAPIS.

Operation details are missing

Run getApiOverview again and copy the exact operationId or route shown in the overview.

Swagger conversion fails

Prefer an OpenAPI 3.x spec URL when available. Swagger 2.0 specs may need conversion before operation details can be returned.

The output is too large

Ask for one operation at a time. The server rejects very large overview output instead of returning an oversized response.

Sources

• OpenAPI MCP Server source
• OpenAPI MCP Server README
• OpenAPI Search
• OAPIS
• OpenAPI Search source
• OAPIS source