A Rust MCP (Model Context Protocol) server that dynamically converts OpenAPI specifications into MCP tools.

• Dynamic Tool Generation: Automatically converts OpenAPI 3.0 operations into MCP tools
• Multiple Transport Support: Supports loading OpenAPI specs from local files or remote URLs
• Flexible Configuration: All configuration via environment variables
• Authentication Support: Supports Bearer token and API key authentication
• YAML & JSON Support: Automatically detects and parses both YAML and JSON OpenAPI specs
• Error Handling: Automatically fixes common OpenAPI spec issues (e.g., numeric values in boolean fields)

cargo build --release

The executable will be at target/release/openapi-mcp-bridge.exe

Configure the server using environment variables:

• OPENAPI_SPEC_PATH: Path or URL to your OpenAPI specification file
  • Local file: ./openapi.json or /path/to/spec.yaml
  • Remote URL: https://api.example.com/openapi.json

• API_BASE_URL: Base URL for API requests (e.g., https://api.example.com)
  • If your OpenAPI spec already includes servers, this can be omitted
• API_AUTH_TOKEN: Bearer token for authentication
  • Adds Authorization: Bearer <token> header to all requests
• API_KEY: API key for authentication
  • Adds X-API-Key: <key> header to all requests
• SKILLS_MD_PATH: Path to a skills.md file for tool defaults (future feature)

# Set environment variables
export OPENAPI_SPEC_PATH="./openapi.json"
export API_BASE_URL="https://api.example.com"
export API_AUTH_TOKEN="your-bearer-token"

# Run the server
./target/release/openapi-mcp-bridge

Add to your Claude Desktop configuration (claude_desktop_config.json):

{
  "mcpServers": {
    "openapi-bridge": {
      "command": "path/to/openapi-mcp-bridge.exe",
      "env": {
        "OPENAPI_SPEC_PATH": "https://api.example.com/openapi.json",
        "API_BASE_URL": "https://api.example.com",
        "API_AUTH_TOKEN": "your-bearer-token"
      }
    }
  }
}

1. On Startup: The server loads the OpenAPI specification from the specified path/URL
2. Tool Discovery: Each GET and POST operation in the spec becomes an MCP tool
   • Tool names are derived from operationId (e.g., getUsers, createOrder)
   • Tool descriptions come from summary or description fields
3. Tool Execution: When Claude calls a tool:
   • The server constructs the full URL using API_BASE_URL + operation path
   • Adds authentication headers if configured
   • For GET requests: query parameters from tool arguments
   • For POST requests: request body from tool arguments
   • Returns the API response to Claude

openapi: 3.0.0
info:
  title: Sample API
  version: 1.0.0
servers:
  - url: https://api.example.com/v1
paths:
  /users:
    get:
      operationId: getUsers
      summary: Get all users
      parameters:
        - name: limit
          in: query
          schema:
            type: integer
        - name: offset
          in: query
          schema:
            type: integer
      responses:
        '200':
          description: Success
    post:
      operationId: createUser
      summary: Create a new user
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                name:
                  type: string
                email:
                  type: string
      responses:
        '201':
          description: Created

This would generate two MCP tools:

• getUsers: GET /users with optional limit/offset parameters
• createUser: POST /users with name/email body parameters

cargo test

RUST_LOG=debug cargo run

cargo build --release

Currently supports:

• ✅ GET and POST operations
• ✅ Query parameters (GET)
• ✅ JSON request bodies (POST)
• ✅ Bearer token authentication
• ✅ API key authentication
• ✅ Local file and remote URL specs
• ✅ YAML and JSON formats

Coming soon:

• 🔲 PUT, DELETE, PATCH operations
• 🔲 Path parameters
• 🔲 Headers from OpenAPI spec
• 🔲 Request validation against schemas
• 🔲 Skills.md integration

This error occurs when the OpenAPI spec uses numeric values (like 0.0 or 1.0) instead of true/false for boolean fields. The server automatically fixes these issues:

• Converts 0.0 → false and any non-zero number → true
• Fixes common boolean fields: deprecated, required, nullable, readOnly, writeOnly, uniqueItems

If you see this error in logs, the server will attempt to fix it automatically and should work correctly.

1. Check your OpenAPI spec URL: Ensure OPENAPI_SPEC_PATH is accessible
2. Enable debug logging: Set RUST_LOG=debug to see detailed error messages
3. Test the URL: Verify you can access the spec in a browser or with curl
4. Check authentication: Ensure API_AUTH_TOKEN or API_KEY are correct if required

Run with verbose logging:

export RUST_LOG=debug
./target/debug/openapi-mcp-bridge.exe

This will show:

• Spec loading process
• Number of tools extracted
• API requests being made
• Detailed error messages

src/
├── main.rs        # Entry point, sets up MCP server with stdio transport
├── lib.rs         # MCP handler implementation (list_tools, call_tool)
├── config.rs      # Environment variable configuration
├── state.rs       # Shared state (tools list, HTTP client, config)
├── openapi.rs     # OpenAPI spec loading and tool extraction
└── tools.rs       # Tool execution logic (makes HTTP requests)

MIT

Contributions welcome! Please open an issue or submit a pull request.