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

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.

1. 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).