onecall-mcp

An MCP (Model Context Protocol) server exposing 10 production-tested no-auth public APIs as tools for AI agents.

Built on top of onecall. Zero API keys. Stdlib Python. MIT.

weather_current(location)              # wttr.in
weather_forecast(lat, lon, days)       # open-meteo
fx_convert(amount, from, to)           # frankfurter (ECB)
fx_rates(base, symbols)                # frankfurter
crypto_price(ids, vs_currency)         # coingecko
geocode(query, limit)                  # openstreetmap nominatim
country_info(query)                    # REST Countries
time_in_zone(timezone)                 # timeapi.io
hn_front()                             # Hacker News top 10
hn_search(query, limit)                # Hacker News Algolia search

Why this exists

Most AI agents need to call weather, FX, crypto, geocoding, time, country, and news lookups. The data is on the open web for free. But the agent needs tools, not URLs. This server gives any MCP-compatible client (Claude Desktop, Cursor, Windsurf, Cline, OpenAI Codex CLI, etc.) all 10 in one process.

Related MCP server: tes-mcp-server

Install

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "onecall": {
      "command": "python3",
      "args": ["/path/to/onecall-mcp/src/onecall_mcp_server.py"]
    }
  }
}

Cursor

Settings → Features → Model Context Protocol → Add new global MCP server. Same command/args.

Windsurf / Cline / others

Same shape — command is the python interpreter, args is the absolute path to onecall_mcp_server.py.

Verify

# End-to-end JSON-RPC over stdio test
bash tests/mcp_stdio_smoke.sh

Last run: 10/10 PASS (2026-08-26). Initialize, tools/list, tools/call all return correct JSON-RPC 2.0 with live API data.

Architecture

• stdlib only. No mcp package dependency, no requests, no SDK. Just urllib + json + asyncio.

• stdio JSON-RPC 2.0. Per MCP spec 2024-11-05.

• Reuses onecall's _lib/http.py for retries, URL encoding, uniform envelope.

• --demo flag prints the tool catalog + runs one live call, useful for sanity checks.

Smoke-test receipts (2026-08-26)

=== Passed: 10  Failed: 0 ===

10 assertions covering: protocol handshake, capability negotiation, tool discovery, tool invocation, live API response.

Roadmap

• Add the remaining 4 onecall wrappers (sunrise, catfact, cataas, nager holidays)

• HTTP transport (currently stdio only)

• Per-call usage tracking + x402 stablecoin paywall integration

• Listing on glama.ai, smithery.ai, mcpmarket.com, mcpservers.org

License

MIT.