# Syntropic

> Small, sharp APIs for developers and AI agents.

Auth: X-API-Key header (prepaid credits, buy at /pricing).

## APIs
- [Travel Per Diem & Allowance Calculator](https://syntropicapi.com/apis/travel-per-diem): Compliant per diems in one call: official US GSA, German BMF and UK HMRC rates, with a trip calculator that applies each country's rules.
  OpenAPI: https://syntropicapi.com/openapi/travel-per-diem.json · MCP: https://syntropicapi.com/mcp/travel-per-diem/mcp