ratebook-mcp

MCP server exposing the Ratebook tariff database and rate engine to apps, devices, and agents. It answers "what will this kWh cost me, and when should I charge?" over the loaded corpus (data/ratebook.duckdb) and the deterministic ratebook engine.

mcp-name: io.github.cbetz/ratebook

Tools

Every Decimal is returned as a string (the engine's canonical wire form), so responses are directly JSON-serializable. "Unknown" is a first-class answer: an unpriceable plan returns a typed refusal, never a wrong number.

Run

uv run ratebook-data urdb     # build data/ratebook.duckdb first (once)
uv run ratebook-mcp           # stdio MCP server

Set RATEBOOK_DB to point at a corpus elsewhere. Register with an MCP client (e.g. Claude Desktop / Code) as a stdio server running ratebook-mcp from a directory containing the DB:

{
  "mcpServers": {
    "ratebook": { "command": "uv", "args": ["run", "ratebook-mcp"], "cwd": "/path/to/ratebook" }
  }
}

The logic lives in ratebook_mcp.service (unit-testable without a running server); server.py is the thin FastMCP binding.