APILinter MCP Server

APILinter MCP Server

The OpenAPI MCP Server powers seamless communication between LLM and REST APIs by implementing the Model Context Protocol (MCP).

Features

Capability	Implemented	Notes
Structured Logging	✅
Metrics & Monitoring	✅
Circuit Breakers	✅
Retry Pattern	✅
Health Checks	✅
API Documentation	❌	Planning
Rate Limiting	❌	Planning
Security Controls	❌
Error Handling	✅
OpenTelemtry	❌	Planning

MCP Protocol Compliance

Feature	Implemented	Notes
Protocol Specification	✅	v2025-03-26
MCP Authentication	❌	not necessary
Session Managment	❌	Stateless
Tools Support	✅	validate_api_specification list_rules calculate_api_quality_score get_rule_categories get_api_docs get_api_linter_link
Resources Support	❌
Prompts Support	✅	api_design_review
Streamable HTTP Transport	✅
SSE Transport	❌	not planing
STDIO Transport	❌	not planing
SDK Client	✅	https://github.com/jbovet/zally-mcp-server.git

Installation

1. Clone the repository:

   git clone [email protected]:jbovet/zally-mcp-server.git
   cd zally-mcp-server

Project Structure:

• src/: Contains the TypeScript source code.
  • circuitbreaker/: Circuitr breaker and retry implementation.
  • config/: Configuration files.
  • controllers/: Express controllers, including the StreamableHttp controller.
  • models/: TypeScript interfaces for data models.
  • repositories/: Data access layer for API Linter.
  • services/: Business logic for API Linter and MCP integration.
  • utils/: Utility classes, including HTTP clients and error handling.
  • target/: Compiled JavaScript files.
• package.json: Project metadata and dependencies.
• tsconfig.json: TypeScript configuration file.
• curl-mcp-client.sh: Bash script to test MCP server endpoints via curl.
• README.md: Project documentation.

1. Install dependencies:

npm install

2. Build the project:

npm run build

Configuration

Environment variables:

• PORT: Server port (default: 3000)
• APILINTER_URL: API Linter service URL (default: http://localhost:3000)
• RETRY_COUNT: Number of retry attempts for failed requests (default: 3)
• CIRCUIT_BREAKER_THRESHOLD: Failure threshold to trigger the circuit breaker (default: 5)

Running the Server

NOTE: before, you need run Zally Server, you can check the doc here https://github.com/zalando/zally?tab=readme-ov-file#quick-start-guide

Start the server with:

npm run dev

The MCP Server will run in Streamable HTTP mode on endpoint: http://localhost:3000/mcp

Testing the Server

Run the tests with:

npm run test

Running the Example Client

To run the example interactive client for the MCP server, use the following command:

npx tsx example/simpleStreamableHttp.ts

This will start the interactive client, allowing you to test various commands and features of the MCP server.

> list-rules
> list-rules true
> validate-api ./my-api-spec.yaml
> validate-api-rules ./my-api-spec.json id

Tools

The MCP server provides the following tools for API Linting:

• validate_api_specification: Validates an API specification (OpenAPI/Swagger) against API Linter rules

  • Parameters: spec (API specification content), ruleIds (optional list of rule IDs to use)
  • Returns: Validation results with violations and formatting
  • Retry Logic: Retries validation requests in case of transient failures
  • Circuit Breaker: Stops validation requests if the API Linter service becomes unresponsive

• list_rules: Lists all available API Linter rules

  • Parameters: isActive (optional boolean to filter by active status)
  • Returns: List of available linting rules with their details
  • Retry Logic: Retries rule listing requests in case of transient failures
  • Circuit Breaker: Prevents further requests if the API Linter service exceeds failure thresholds

• calculate_api_quality_score: Calculates the quality score of an API specification

  • Parameters: spec (API specification content)
  • Returns: Quality score with detailed breakdown

• get_rule_categories: Retrieves the categories of API Linter rules

  • Parameters: None
  • Returns: List of rule categories

Prompts

The MCP server provides the following pre-configured prompts:

• api_design_review: Analyzes an API specification and provides comprehensive design feedback
  • Parameters:
    • specification (API specification content in JSON or YAML format)
    • focusAreas (optional comma-separated list of areas to focus on, e.g., "security,naming,consistency")
  • Returns: Structured API design feedback including:
    • Executive summary of API purpose and design
    • Strengths identification
    • Areas for improvement (naming, consistency, error handling, security, etc.)
    • Specific recommendations for API enhancement

Security Notes

• Implements origin validation to prevent DNS rebinding attacks
• Uses Streamable HTTP transport in stateless mode for security
• Only processes requests from trusted origins (localhost) in development
• All API inputs are validated before processing
• Retry Logic and Circuit Breaker: Enhance resilience and security by handling service failures gracefully

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Install dependencies (npm install)
4. Make your changes
5. Run tests to ensure they pass (npm test)
6. Commit your changes (git commit -m 'Add some amazing feature')
7. Push to the branch (git push origin feature/amazing-feature)
8. Open a Pull Request

License

This project is licensed under the MIT License. See the LICENSE file for details.