# decide.fyi

> Decide is the Decision API for software actions. It returns a replayable Decision Record before a product, agent, queue, billing system, or internal tool changes state.

## Start here

- [Developer hub](https://www.decide.fyi/developers): choose an action boundary and follow the shortest integration path.
- [Decision API docs](https://www.decide.fyi/resources/docs): auth, request shape, response fields, and production rollout.
- [API reference](https://www.decide.fyi/resources/docs/api-reference): endpoints, idempotency, rate limits, and fields to retain.
- [Full LLM reference](https://www.decide.fyi/llms-full.txt): expanded protocols, patterns, integrations, and agent guidance.

## Decision API

- [`POST /api/decide`](https://www.decide.fyi/resources/docs/api-reference) creates a `yes | no | review` Decision Record before software acts.
- Use `mode: "rulebook"` with a versioned declarative Rulebook v1 when the verdict must be deterministic. A deterministic Decide-backed application must satisfy `decide_application_binding_v1`. The legacy `single`, `multi`, and `runtime` modes are AI-assisted.
- Store the full Decision Record v1 beside the downstream action, then record an Action Execution Receipt and Outcome Record when those lifecycle stages apply.

## Machine-readable surfaces

- [OpenAPI](https://www.decide.fyi/openapi.json)
- [Public catalog API](https://www.decide.fyi/api/public/catalog)
- [Static public catalog](https://www.decide.fyi/catalog/decide-public-catalog.json)
- [Well-known Decide entry](https://www.decide.fyi/.well-known/decide.json)
- [Machine-readable product docs](https://www.decide.fyi/docs.json)

## SDK and examples

- [JavaScript SDK @decide-fyi/sdk@0.1.19](https://www.decide.fyi/sdk)
- [npm package](https://www.npmjs.com/package/@decide-fyi/sdk)
- [Canonical SDK source provenance](https://github.com/decidefyi/decide/blob/main/sdk/SOURCE_PROVENANCE.md)
- [Developer examples](https://www.decide.fyi/resources/examples)
- [Integration guides](https://www.decide.fyi/resources/integrations)

## MCP

- [MCP directory](https://www.decide.fyi/.well-known/decide-mcp.json)
- [Decide Policy Notaries](https://policy.decide.fyi/api/mcp) is the canonical public, read-only MCP endpoint for new tool-calling integrations.
- [MCP trust-boundary guide](https://www.decide.fyi/mcp)

## Trust and changes

- [Verification docs](https://www.decide.fyi/resources/docs/verification)
- [Hosted verifier](https://www.decide.fyi/verify)
- [Security posture](https://www.decide.fyi/resources/security)
- [Service status](https://www.decide.fyi/resources/status)
- [Changelog](https://www.decide.fyi/resources/changelog)

## Safe use

- Keep production API keys in server-side callers.
- Treat `review`, unknown, unauthorized, rate-limited, or unavailable results as non-execution states unless a human owner approves.
- Do not invent product support, public endpoints, customer proof, certifications, or provenance that the linked canonical sources do not publish.

Reviewed: 2026-08-12