prt-mcp

MCP server exposing Pittsburgh Regional Transit (PRT) TrueTime operations as typed tools for agent clients.

What this implements

• MCP tools for core TrueTime queries:

  • prt_get_routes

  • prt_get_directions

  • prt_get_stops

  • prt_get_vehicles

  • prt_get_predictions

  • prt_get_patterns

  • prt_get_service_bulletins

• MCP resources:

  • prt://capabilities (discoverability for clients)

• MCP prompts:

  • transit-arrival-workflow

Related MCP server: marta-mcp

Source references used for design

• MCP protocol/spec and server guidance:

  • modelcontextprotocol.io docs + specification (JSON-RPC, capabilities, safety)

• MCP reference implementations:

  • modelcontextprotocol/servers (everything, fetch, filesystem)

• MCP SDK patterns:

  • modelcontextprotocol/typescript-sdk

• PRT data/API entry points:

  • PRT Developer Resources

  • TrueTime account/API key workflow

  • TrueTime v3 endpoint behavior from public community codebases:

    • juctaposed/bustimePGH

    • aidan2312/prt-api

Prerequisites

• Node 20+ (Node 22 recommended)

• A PRT TrueTime API key

Configuration

Copy env template:

cp .env.example .env

Set:

• PRT_TRUETIME_API_KEY (required)

• Optional tuning:

  • PRT_TRUETIME_BASE_URL

  • PRT_REQUEST_TIMEOUT_MS

  • PRT_MAX_RETRIES

  • PRT_USER_AGENT

• Optional HTTP mode security:

  • HOST (default: 127.0.0.1)

  • PORT (default: 3000)

  • MCP_ALLOWED_HOSTS (comma-separated Host allowlist)

  • MCP_ALLOWED_ORIGINS (comma-separated browser Origin allowlist)

  • MCP_AUTH_TOKEN (Bearer token expected on /mcp)

  • MCP_RATE_LIMIT_WINDOW_MS

  • MCP_RATE_LIMIT_MAX

Run

npm install
npm run build
npm start

For local development:

npm run dev

For hosted HTTP mode (remote MCP endpoint):

npm run build
PORT=3000 HOST=0.0.0.0 MCP_AUTH_TOKEN=change-me npm run start:http

Health check:

curl http://localhost:3000/healthz

MCP endpoint:

• POST /mcp

• GET /mcp (SSE stream)

• DELETE /mcp (close session if stateful)

• Include Authorization: Bearer <MCP_AUTH_TOKEN> if auth is enabled.

Alternate SSE endpoint for clients that expect /sse:

• POST /sse

• GET /sse (SSE stream)

• DELETE /sse (close session if stateful)

Example MCP client config (stdio)

{
	"mcpServers": {
		"prt": {
			"command": "node",
			"args": ["/ABSOLUTE/PATH/prt-mcp/dist/index.js"],
			"env": {
				"PRT_TRUETIME_API_KEY": "YOUR_KEY"
			}
		}
	}
}

Hosting options

You now have two transport modes:

1. Local stdio (npm start)
   Best for Claude Desktop / local agent tools.

2. Remote Streamable HTTP (npm run start:http)
   Best for hosting on Render/Railway/Fly.io/a VM.

Minimal production checklist:

• Set PRT_TRUETIME_API_KEY in host environment variables.

• Use Node 20+ runtime.

• Expose the PORT your host provides.

• Keep at least one health check path (/healthz).

• Set MCP_AUTH_TOKEN.

• Set MCP_ALLOWED_HOSTS and MCP_ALLOWED_ORIGINS for your deployment.

• Restrict inbound access (IP allowlist, auth gateway, or private network).

Example Render/Railway start command:

npm run build && npm run start:http

Docker

Build image:

docker build -t prt-mcp:latest .

Run container:

docker run --rm -p 3000:3000 -e PRT_TRUETIME_API_KEY=YOUR_KEY prt-mcp:latest

Implementation best practices applied

• Input validation with zod on every tool schema

• Fail-fast config checks (missing key)

• Retry + timeout behavior to handle unstable upstream API responses

• Uniform structured + text output for deterministic agent parsing

• Tool execution failures returned as MCP isError results

• Tool annotations (readOnlyHint, idempotentHint, openWorldHint) for client safety hints

• HTTP hardening: auth token, origin checks, host allowlist support, and rate limiting

• Strict TypeScript + minimal surface area

• No secrets in source; env-only configuration

Notes

• TrueTime key acquisition is account-gated by PRT.

• API responses can differ by data feed (Port Authority Bus, Light Rail).

• Some endpoints require additional filters (rt, stpid, pid).