For product teams building tax workflows inside a published supported envelope. Tax MCP computes when the case is modeled, returns a deterministic unsupported or needs_review decline when it is not, and makes billing and retry behavior explicit. No LLM in the loop — same input, same output, every time; primary-source-backed, reproducible, auditable.
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No model in the loop — a table-driven, §6694-disciplined engine, not an LLM. Every figure is primary-source-backed and carries its own derivation; ambiguous cases decline with a reason instead of a wrong-but-plausible guess. Reproducible and auditable, with no per-call model cost.
Send an Idempotency-Key and retries replay the byte-identical response, billed exactly once. Quota and per-minute rate limits fail closed.
Supported today: standard-deduction W-2 wage workflows with documented interest / dividend and clean capital-gain facts, across selected federal and CA / NY / NYC paths. Full-return preparation, credits, and filing are out of scope and decline deterministically (itemized is supported for SALT + mortgage interest) — see the supported-vs-declined reference.
The boundary is published, not discovered at runtime. Anything on the right returns a deterministic 200 decline (a reason + next_action), never a wrong-but-plausible number. Machine-readable at /api/mcp/tax-capabilities.
A few near-term themes below. The full complete-tax-engine roadmap — every feature, with shipped / certifying / planned status — lives on the roadmap page(a proposed working order, independently reviewed before it's locked). If you think something should move up, tell us on feedbackand we'll use it to reorder the next slice.
Finalize the legal notice shape and publish binding terms only after the founder legal facts are cleared.
Give users a direct way to tell us what is blocking adoption, what should move up, and what should be clarified next.
Make the first successful call easier with clearer setup, decline interpretation, and next-step guidance.
Let users upload source documents and receive a structured JSON envelope they can inspect, store, and pass downstream.
Expand the docs, marketplace copy, and supported envelope only after the higher-priority trust and adoption gaps are addressed.
Bearer token on every request.