OpenAPI → MCP Server

Convert any OpenAPI specification into an MCP server that AI agents can use. Instead of registering one tool per endpoint (which bloats agent context), this server exposes just two tools:

This keeps the agent's context small (~1,200 tokens) regardless of how many endpoints the API has.

How It Works

┌─────────────┐     ┌──────────────────┐     ┌──────────┐
│  AI Agent    │────▶│  MCP Server      │────▶│ REST API │
│  (Claude,    │◀────│                  │◀────│ (Salla)  │
│   Cursor,..) │     │  search: query   │     └──────────┘
│              │     │    OpenAPI spec   │
│              │     │  execute: proxy   │
│              │     │    HTTP + auth    │
└─────────────┘     └──────────────────┘

1. At startup, the server loads openapi.json and indexes all paths in memory
2. search("products") — scans the spec and returns matching endpoints with their parameters, methods, and descriptions
3. execute("/products", "GET", parameters={"page": 1}) — makes the actual HTTP call to the API, injecting the Bearer token automatically
4. The agent never sees the full spec — it discovers what it needs on demand

Quick Start

# Install
pip install -e .

# Configure
cp .env.example .env
# Edit .env → set SALLA_API_TOKEN

# Run (stdio for MCP clients like Claude Desktop, VS Code)
python server.py

# Run as HTTP server (for direct agent access)
python server.py streamable-http

Transport Modes

HTTP Mode

When running with streamable-http, the server listens on http://0.0.0.0:8000/mcp by default. Configure with environment variables:

SERVER_HOST=0.0.0.0
SERVER_PORT=8000

Configuration

All via environment variables (or .env file):

Using with AI Agents

Claude Desktop / Claude Code

Add to your MCP config (claude_desktop_config.json or .claude.json):

{
  "mcpServers": {
    "salla-api": {
      "command": "python",
      "args": ["server.py"],
      "cwd": "/path/to/fastmcp-openapi-spec"
    }
  }
}

Then ask Claude:

"Search for product endpoints and list the first 5 products"

Claude will:

1. Call search("products") → discovers GET /products, POST /products, etc.
2. Call execute("/products", "GET", parameters={"limit": 5}) → gets the data
3. Present the results

Direct HTTP Access (for custom agents)

Start the server in HTTP mode:

python server.py streamable-http

Then any AI agent or application can connect using the MCP protocol over HTTP at http://localhost:8000/mcp.

Python agent example (using mcp client SDK):

from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client

async def main():
    async with streamablehttp_client("http://localhost:8000/mcp") as (r, w, _):
        async with ClientSession(r, w) as session:
            await session.initialize()

            # Discover endpoints
            result = await session.call_tool("search", {"query": "orders"})
            print(result)

            # Execute an API call
            result = await session.call_tool("execute", {
                "endpoint": "/orders",
                "method": "GET",
                "parameters": {"page": 1, "limit": 10}
            })
            print(result)

cURL example (raw MCP-over-HTTP):

# Initialize session
curl -X POST http://localhost:8000/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'

# Call the search tool
curl -X POST http://localhost:8000/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"search","arguments":{"query":"products","limit":5}}}'

VS Code Copilot Agent Mode

Add to .vscode/mcp.json:

{
  "servers": {
    "salla-api": {
      "command": "python",
      "args": ["server.py"],
      "cwd": "${workspaceFolder}"
    }
  }
}

Cursor

Add to .cursor/mcp.json:

{
  "mcpServers": {
    "salla-api": {
      "command": "python",
      "args": ["server.py"],
      "cwd": "/path/to/fastmcp-openapi-spec"
    }
  }
}

Agent Workflow Examples

Example 1: Browse products

Agent                          MCP Server                    Salla API
  │                               │                             │
  │ search("products")            │                             │
  │──────────────────────────────▶│                             │
  │   [{path:"/products",         │                             │
  │     method:"GET", ...}]       │                             │
  │◀──────────────────────────────│                             │
  │                               │                             │
  │ execute("/products","GET",    │  GET /v2/products?limit=5   │
  │   {limit:5})                  │────────────────────────────▶│
  │                               │   {products: [...]}         │
  │   {status:"success",          │◀────────────────────────────│
  │    data:{products:[...]}}     │                             │
  │◀──────────────────────────────│                             │

Example 2: Create an order

User: "Create an order for customer 123 with product SKU-456"

Agent thinks: I need to find the create order endpoint first.

→ search("create order")
← [{path: "/orders", method: "POST", requestBody: {required: ["customer_id", "items"]}}]

Agent thinks: Now I know the endpoint and required fields.

→ execute("/orders", "POST", body={"customer_id": 123, "items": [{"sku": "SKU-456", "quantity": 1}]})
← {status: "success", statusCode: 201, data: {id: 789, status: "pending"}}

Agent: "Order #789 created successfully for customer 123."

Example 3: Multi-step investigation

User: "What's the status of order 789 and who placed it?"

→ search("order")
← [GET /orders/{id}, GET /orders, POST /orders, ...]

→ execute("/orders/789", "GET")
← {data: {id: 789, status: "shipped", customer_id: 123}}

→ search("customer")
← [GET /customers/{id}, ...]

→ execute("/customers/123", "GET")
← {data: {id: 123, name: "Ahmad", email: "ahmad@example.com"}}

Agent: "Order 789 is shipped. It was placed by Ahmad (ahmad@example.com)."

Adapting for Other APIs

This server works with any OpenAPI 3.x spec. To use it with a different API:

1. Replace openapi.json with your API's spec
2. Update .env with your API's base URL and auth token:

   SALLA_BASE_URL=https://api.yourservice.com/v1
   SALLA_API_TOKEN=your-token
   

3. Run python server.py

The search and execute tools automatically adapt to whatever endpoints are defined in the spec.

Project Structure

server.py          ← entry point (registers tools, runs transport)
src/
  config.py        ← env vars + OpenAPI spec loading
  tools.py         ← search and execute tool implementations
openapi.json       ← your API specification
.env.example       ← configuration template
pyproject.toml     ← dependencies

License

MIT