Changelog
What's shipped and live on the Tax MCP compute API. Contract-affecting changes are versioned in the OpenAPI spec; the live supported envelope is always at tax-capabilities.
Public compute API — GA candidate
2026-07-01
- Deterministic federal 1040 compute: ordinary tax, NIIT (Form 8960), Additional Medicare (Form 8959), preferential LTCG / qualified-dividend bands — standard deduction, whole-dollar per the form's rounding.
- State compute: selected CA 540 and NY / NYC 2025 paths; decline-aware CA reconcile against a filed return (non-mutating).
- Coverage-bounded by design: outside the modeled envelope the engine returns a deterministic 200 decline (code + reason + next_action), never a wrong-but-plausible number.
- Machine-readable discovery: GET /api/mcp/tax-capabilities advertises the per-jurisdiction supported envelope, decline codes, review states, and billing semantics — no taxpayer payload required.
- Uniform response contract on every response: billed (ledger truth), retry_safe, next_action, reason, and provenance on computed results — identical across OpenAPI, docs, and live.
- Idempotency-Key: a retry with the same key + body replays the byte-identical first response and bills exactly once.
- Billing that fails closed: monthly quota is a hard 429 cap (no surprise overage); per-minute rate limits return 429; usage headers (X-Quota-*, X-RateLimit-*) let you back off before a limit.
- Runnable quickstart with a real deterministic-decline example, plus the full OpenAPI 3.1 spec at /api/openapi.json.
- Canonical host tax-mcp.com.