Python API — design and build (FastAPI + async ORM)

This skill produces a working, deployable API — not a tutorial. It has two halves:

• Sections 0–2 — design. What the API promises, how it is versioned, and what changes when the domain is not a blog.
• Sections 3–21 — build. One skeleton, one set of conventions, and the handful of decisions that must be asked instead of assumed (Appendix A).

Rules are IDs (DES-3, CFG-1, EP-4, …) so they can be referenced in review. Appendices B–F trace every rule back to evidence; Appendix G explains the limits of that evidence.

Nothing in the build half is mandatory. Each layer — database, migrations, auth, uploads, email, frontend, containers, CI, health checks — exists only if the target API has that requirement. Section 1 starts with the decision table; read it before generating anything.