Swagger API MCP Server

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An MCP (Model Context Protocol) server that parses Swagger 2.0 and OpenAPI 3.x specifications, exposing API structure through MCP tools. Features a local file-cache architecture that reduces token usage by 85-95% compared to inline responses.

Features

• Swagger 2.0 & OpenAPI 3.x — Full dual-format support
• Smart Caching — Spec parsed once, stored as local JSON files; tools return compact summaries + file paths (~200 chars vs 5-20KB)
• 11 MCP Tools — Load, browse, search, call APIs, and manage auth dynamically
• 3 MCP Prompts — Guided workflows for exploring, searching, and integrating APIs
• 3 MCP Resources — Direct access to cached API info, endpoints, and schemas
• Two Transport Modes — stdio (for CLI/IDE integration) and HTTP (for multi-session web use)
• 2-Phase API Calls — Preview requests before executing them
• Zero External Parsers — Custom $ref resolver with circular reference protection

Prerequisites

• Node.js >= 24

Quick Start

Install from npm

npm install -g swagger-api-mcp-server

Or clone and build

git clone https://github.com/NekoTarou/swagger-api-mcp-server.git
cd swagger-api-mcp-server
npm install
npm run build

Run

# stdio mode (default) — for MCP clients like Claude Desktop
npm start

# Auto-load a spec on startup
SWAGGER_URL=https://petstore.swagger.io/v2/swagger.json npm start

# HTTP mode — multi-session with Express
npm run start:http

MCP Client Configuration

Claude Desktop

Add to your Claude Desktop config file (claude_desktop_config.json):

{
  "mcpServers": {
    "swagger-api": {
      "command": "npx",
      "args": ["-y", "swagger-api-mcp-server"],
      "env": {
        "SWAGGER_URL": "https://petstore.swagger.io/v2/swagger.json"
      }
    }
  }
}

Cursor / VS Code

Add to your MCP settings:

{
  "mcpServers": {
    "swagger-api": {
      "command": "npx",
      "args": ["-y", "swagger-api-mcp-server"],
      "env": {
        "SWAGGER_URL": "https://your-api.example.com/openapi.json"
      }
    }
  }
}

Tools

Tool	Description
swagger_load_spec	Load a Swagger/OpenAPI spec from URL, parse and cache it
swagger_update_cache	Re-fetch spec and rebuild cache
swagger_get_info	Get API metadata (title, version, servers, auth schemes)
swagger_list_tags	List all tags with endpoint counts
swagger_list_paths	List endpoints with filtering (tag, method, keyword) and pagination
swagger_get_endpoint	Get endpoint summary + cached file path for full details
swagger_list_schemas	List schema definitions with filtering and pagination
swagger_get_schema	Get schema summary + cached file path for full definition
swagger_search	Search across endpoints and schemas by keyword
swagger_call_api	Execute HTTP requests with 2-phase confirmation
swagger_set_auth	Dynamically set or clear the Authorization header at runtime

Prompts

Prompt	Arguments	Description
swagger_explore_api	url	Guided workflow to load and fully explore an API spec
swagger_find_endpoint	keyword	Search for endpoints by keyword and view full details
swagger_integrate_api	url, task	Find the right endpoint for a task and execute an API call

Resources

Resource	URI	Description
api-info	swagger://api/info	API basic information (title, version, servers, auth)
api-endpoints	swagger://api/endpoints	Index of all API endpoints
api-schemas	swagger://api/schemas	Index of all schema/model definitions

Cache Architecture

When a spec is loaded, it's parsed once and stored as structured JSON files:

.swagger-cache/
├── meta.json              # Cache metadata (URL, counts, timestamp)
├── info.json              # Full API info (title, servers, auth)
├── tags.json              # Tag list with endpoint counts
├── paths-index.json       # Endpoint index for fast lookup
├── schemas-index.json     # Schema index for fast lookup
├── endpoints/             # One file per endpoint (deep-resolved)
│   └── GET__users__{id}.json
└── schemas/               # One file per schema (deep-resolved)
    └── User.json

Tools return brief summaries with file paths. The LLM reads full details on demand via the Read tool — saving 85-95% of tokens per call.

Environment Variables

Variable	Default	Description
SWAGGER_URL	(empty)	Auto-load spec on startup
TRANSPORT	stdio	Transport mode: stdio or http
MCP_PORT	3000	HTTP server port
MCP_HOST	0.0.0.0	HTTP server host
API_BASE_URL	(empty)	Override API base URL for calls
API_AUTH_TOKEN	(empty)	Initial Authorization header value (can be updated at runtime via swagger_set_auth)
CACHE_DIR	.swagger-cache	Custom cache directory path
SESSION_TIMEOUT_MS	1800000	HTTP session timeout (30 min)
MAX_SESSIONS	100	Max concurrent HTTP sessions

Development

npm run dev            # Dev mode with auto-reload (tsx watch)
npm test               # Run tests
npm run build          # TypeScript compilation → dist/
npm run clean          # Remove dist/

License

MIT