mcp-openapi

mcp-openapi

    

Turn any OpenAPI spec into MCP tools for Claude — zero config, instant API access.

Point mcp-openapi-runner at any OpenAPI 3.x spec and Claude can call every endpoint through natural language. No custom integration code. No manual tool definitions. One line of config.

Why mcp-openapi?

| Without mcp-openapi | With mcp-openapi | |---|---| | Write custom MCP server per API | One config line per API | | Define tool schemas manually | Auto-generated from OpenAPI spec | | Handle auth, params, body yourself | Built-in auth + parameter handling | | Maintain code as API evolves | Spec changes = tools update automatically |

Quick start

Add to your Claude Desktop / Claude Code / Cursor / Cline MCP config:

{
  "mcpServers": {
    "petstore": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner", "--spec", "https://petstore3.swagger.io/api/v3/openapi.json"]
    }
  }
}

That's it. Claude can now discover and call every endpoint in that API.

Example conversation

You: What pets are available? Add a new dog named Buddy. Claude: Let me check what's available. [calls list_endpoints → discovers findPetsByStatus, addPet, ...] [calls call_endpoint → findPetsByStatus with status=available] There are 3 pets currently available. Now I'll add Buddy... [calls call_endpoint → addPet with {"name":"Buddy","status":"available"}] Done! Buddy has been added with ID 12345.

Features

• Zero config — just point at a spec URL or file
• Any OpenAPI 3.x spec — JSON or YAML, local or remote, $ref auto-resolved
• Auto-generated operationIds — works even when the spec doesn't define them
• Built-in auth — Bearer, API key, Basic auth via environment variables
• Endpoint filtering — only expose the endpoints you need with --filter
• Custom headers — pass arbitrary headers with --header
• Server URL override — point at staging/local with --server-url
• Two-tool design — simple list_endpoints → call_endpoint workflow
• Works everywhere — Claude Desktop, Claude Code, Cursor, Cline, any MCP client

Ready-to-use configs

Stripe

{
  "mcpServers": {
    "stripe": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner", "--spec", "https://raw.githubusercontent.com/stripe/openapi/master/openapi/spec3.json"],
      "env": {
        "OPENAPI_BEARER_TOKEN": "sk_test_..."
      }
    }
  }
}

GitHub REST API

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner",
        "--spec", "https://raw.githubusercontent.com/github/rest-api-description/main/descriptions/api.github.com/api.github.com.json",
        "--filter", "repos"],
      "env": {
        "OPENAPI_BEARER_TOKEN": "ghp_..."
      }
    }
  }
}

Your internal API

{
  "mcpServers": {
    "internal": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner", "--spec", "http://localhost:8080/openapi.json"],
      "env": {
        "OPENAPI_API_KEY": "dev-key-123"
      }
    }
  }
}

Jira (Atlassian)

{
  "mcpServers": {
    "jira": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner",
        "--spec", "https://dac-static.atlassian.com/cloud/jira/platform/swagger-v3.v3.json",
        "--server-url", "https://your-domain.atlassian.net",
        "--filter", "issue"],
      "env": {
        "OPENAPI_BASIC_USER": "you@company.com",
        "OPENAPI_BASIC_PASS": "your-api-token"
      }
    }
  }
}

Authentication

Pass credentials via environment variables:

{
  "mcpServers": {
    "my-api": {
      "command": "npx",
      "args": ["-y", "mcp-openapi-runner", "--spec", "https://api.example.com/openapi.json"],
      "env": {
        "OPENAPI_BEARER_TOKEN": "your-token-here"
      }
    }
  }
}

| Variable | Description | |---|---| | OPENAPI_BEARER_TOKEN | Bearer token → Authorization: Bearer <token> | | OPENAPI_API_KEY | API key value | | OPENAPI_API_KEY_HEADER | Header name for API key (default: X-Api-Key) | | OPENAPI_BASIC_USER | HTTP Basic auth username | | OPENAPI_BASIC_PASS | HTTP Basic auth password |

CLI options

npx mcp-openapi-runner --spec <url-or-path> [options]

Options:
  --spec         Path or URL to an OpenAPI 3.x spec (JSON or YAML)
  --server-url   Override the base URL from the spec
  --filter       Only expose endpoints matching a pattern (path, tag, or operationId)
  --header       Add custom header to all requests ("Name: Value", repeatable)
  --help         Show help

Examples

# Basic usage
npx mcp-openapi-runner --spec https://petstore3.swagger.io/api/v3/openapi.json

# Only pet-related endpoints
npx mcp-openapi-runner --spec ./openapi.yaml --filter pets

# Point at local dev server
npx mcp-openapi-runner --spec ./openapi.yaml --server-url http://localhost:3000

# Custom headers
npx mcp-openapi-runner --spec ./openapi.yaml --header "X-Tenant: acme" --header "X-Debug: true"

# With auth
OPENAPI_BEARER_TOKEN=mytoken npx mcp-openapi-runner --spec https://api.example.com/openapi.json

Tools

mcp-openapi-runner exposes exactly two tools:

| Tool | Description | |---|---| | list_endpoints | Returns all operations grouped by tag with operationIds, methods, paths, and parameters | | call_endpoint | Executes any operation by operationId with path/query/header/body parameters |

The two-tool design means Claude always has a clear workflow: discover → call.

How it works

1. Loads the OpenAPI spec from the given URL or file path
2. Dereferences all $ref schemas using @apidevtools/swagger-parser
3. Applies endpoint filter if --filter is set
4. Registers two MCP tools with the connected client
5. list_endpoints generates a human+LLM-readable summary of all operations
6. call_endpoint resolves params, builds the URL, attaches auth + custom headers, returns the response

Requirements

• Node.js 18+
• OpenAPI 3.x spec (JSON or YAML, local file or URL)

Contributing

Contributions welcome! See CONTRIBUTING.md for guidelines.

License

MIT