singlefax

SingleFax API versioning and deprecation

Agents and backends can rely on this policy. The current REST surface is /api/v1. There is no sunset scheduled.

Versioning

The public REST API is versioned in the URL path: https://singlefax.com/api/v1/… and the same paths on api.singlefax.com. OpenAPI is /openapi.json with info.version matching the path major (currently 1.0.0).

Additive, backward-compatible changes (new optional fields, new endpoints, new error data.code values) stay on v1 without a header. Breaking changes — removed fields, changed types, or new required auth — ship as /api/v2. We do not silently change v1 request or response shapes.

Deprecation and Sunset

When a v1 operation or field is going away, responses for that operation include RFC 8594 Deprecation (the date we marked it) and RFC 8594 Sunset (the date it will stop working). Sunset is at least 90 days after Deprecation. OpenAPI marks the same operations with deprecated: true.

No v1 operation currently carries Deprecation or Sunset. MCP Streamable HTTP at /mcp follows the same notice window if a tool is removed.

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