opendata-mcp

A Model Context Protocol server for the OpenData Platform API. Tools are generated dynamically from the bundled OpenAPI 3.1 spec — every endpoint is exposed as an MCP tool with a typed input schema and a transparent HTTP handler.

• GET endpoints: 76 — exposed without auth (the API serves them unauthenticated).

• Write endpoints (POST / PUT / PATCH / DELETE): 23 — require a Bearer token via OPENDATA_API_KEY.

• Built on @modelcontextprotocol/sdk (TypeScript) with stdio transport.

Install

Uses pnpm (pinned via packageManager in package.json so corepack enable is enough to get the right version).

pnpm install
pnpm run build

Related MCP server: MCP from API

Configure

Copy .env.example → .env (or set in your MCP client config) and fill in:

OPENDATA_BASE_URL=https://api.tryopendata.ai   # required at call time
OPENDATA_API_KEY=od_live_xxx                   # required for writes
# OPENDATA_READ_ONLY=true                      # optional: only register GET tools
# OPENDATA_TIMEOUT_MS=30000                    # optional: per-request timeout
# OPENDATA_MAX_ATTEMPTS=3                      # optional: total HTTP attempts (retries are bounded; see below)
# OPENDATA_LOG_LEVEL=info                      # optional: off|error|info|debug

Secrets are never read from the repo. .env is gitignored; .env.example ships placeholders only.

Run

# Dev (tsx, no build step)
pnpm run dev

# Production (after build)
pnpm start

The server speaks MCP over stdio — wire it into any MCP-capable client. Example client config (Claude Desktop / similar):

{
  "mcpServers": {
    "opendata": {
      "command": "node",
      "args": ["/absolute/path/to/opendata-mcp/dist/index.js"],
      "env": {
        "OPENDATA_BASE_URL": "https://api.tryopendata.ai",
        "OPENDATA_API_KEY": "od_live_xxx"
      }
    }
  }
}

Test

pnpm test            # unit tests (mocked fetch — offline-safe)
pnpm run typecheck   # tsc --noEmit

Live tests against the real API run only when OPENDATA_BASE_URL is set:

OPENDATA_BASE_URL=https://api.tryopendata.ai pnpm test

CI runs the unit suite on every push/PR (badge above). The live smoke job runs on a daily schedule (and on pushes to main) only if the repo has OPENDATA_BASE_URL (and optionally OPENDATA_API_KEY) configured as Actions secrets — it's continue-on-error: true so a transient upstream outage doesn't show the repo as red.

How tool generation works

At startup the server:

1. Loads openapi.json (OpenAPI 3.1, bundled).

2. Walks every (path, method) pair (skipping deprecated operations and skipping non-GET when OPENDATA_READ_ONLY=true).

3. Converts each operation's path + query parameters (and JSON request body for writes) into a Zod input schema via openapi-to-zod.ts.

4. Registers one MCP tool per operation. The tool name is the OpenAPI operationId (sanitized to [a-zA-Z0-9_-]{1,64}); the description is METHOD path (auth?) — summary — description.

5. On invoke, builds the URL (substituting path params + appending the query string), attaches Authorization: Bearer ${OPENDATA_API_KEY} for non-GET, sends the request, and returns the response as a text MCP content block.

The auth contract is enforced at the client layer (src/api-client.ts):

• GET → no auth header is sent. If you pass a key it's still ignored.

• Non-GET → OPENDATA_API_KEY is required; the request fails fast with a clear error if it's missing.

Logging, retries, and shutdown

• Structured logging to stderr (stdout is reserved for the MCP protocol). One JSON object per line: {ts, level, msg, ...fields}. Tuned via OPENDATA_LOG_LEVEL (off|error|info|debug, default info). Every tool invocation carries a short rid (request id) that also surfaces in any error message returned to the client — so a user can quote an ERROR (rid=…) and you can grep it in logs.

• Bounded retries on transient failures only: 502 / 503 / 504 and network errors are retried with jittered exponential backoff (200ms → 600ms → 1.4s, capped). 500 and any 4xx are never retried — a 500 means "I tried, it broke" and retrying just hammers a server that already gave its answer; a 4xx means the request is wrong and retrying won't help. Total attempts via OPENDATA_MAX_ATTEMPTS (default 3).

• Graceful shutdown on SIGINT / SIGTERM: the MCP transport is closed before process.exit so any in-flight tool calls have a chance to land.

Layout

src/
  index.ts              # entry — MCP server, stdio transport
  openapi-loader.ts     # loads + normalizes the bundled spec
  openapi-to-zod.ts     # OpenAPI schema → Zod schema converter
  api-client.ts         # fetch wrapper + auth contract
  tools.ts              # generates MCP tool defs from normalized ops
  __tests__/
    tools.test.ts       # unit tests (mocked fetch)
    live.test.ts        # live tests (skipped unless OPENDATA_BASE_URL set)
openapi.json            # bundled OpenAPI 3.1 spec

License

MIT