Root Handler

The root handler (server/src/root_handler.rs) has the functions to serve the GET / (Root) endpoint. It returns a plain-text response describing the server and its available data.

Response Contents

The response includes:

1. Usage instructions — how to send queries and a link to the x402 protocol docs.
2. Supported tables — for each table in the payment configuration:
   • Table name
   • Schema (field names and data types), if available
   • Description, if provided
   • Whether payment is required
3. SQL parser rules — the restrictions enforced by the SQL parser:
   • Only SELECT statements
   • One statement per request
   • One table in the FROM clause
   • No GROUP BY, HAVING, JOIN, or subqueries
   • Only simple field names in SELECT (no expressions)
   • WHERE, ORDER BY, and LIMIT supported with restrictions

Purpose

This endpoint is designed for both human users and AI agents to discover what data is available and how to query it before making paid requests.