decide.fyi Decision API

Deterministic Decision API engine powering workflow applications, stable MCP notary remotes, decision memo packets, and execution gates

Positioning: Decide is the API engine and compatibility surface. Krafthaus workflow apps, Policy MCP Notaries, decision memo packets, and execution gates are application surfaces that reuse the same verdict, request ID, and evidence contract.

Production Determinism Boundary

Binding production verdicts should use a versioned declarative rulebook:

Runtime architecture: see docs/RULEBOOK_RUNTIME_ARCHITECTURE.md. Machine-readable schema: https://api.decide.fyi/schemas/rulebook-v1.schema.json. Active runtime manifest: https://api.decide.fyi/manifests/rulebook-runtime-v1.json. Downstream application binding: decide_application_binding_v1.

The production core is hybrid_declarative_rulebook_with_trusted_adapters: direct declarative rulebooks are supported, registered first-party trusted adapters may supply bounded facts, and customer executable rulebooks are rejected. In both supported binding modes, Rulebook v1 remains the only binding verdict selector.

{
  "mode": "rulebook",
  "rulebook": {
    "schema_version": "rulebook_v1",
    "rulebook_id": "pricing_exception",
    "version": "2026-06-11",
    "input_schema": {
      "required": ["discount_percent"],
      "properties": {
        "discount_percent": { "type": "number" }
      }
    },
    "rules": [
      {
        "rule_id": "approve_standard_discount",
        "priority": 50,
        "condition": {
          "field": "discount_percent",
          "operator": "lte",
          "value": 15
        },
        "outcome": {
          "decision": "yes",
          "verdict": "APPROVE",
          "action": "approve_discount",
          "reason_code": "WITHIN_STANDARD_LIMIT"
        }
      }
    ],
    "default_outcome": {
      "decision": "review",
      "verdict": "REVIEW",
      "action": "route_to_owner",
      "reason_code": "NO_RULE_MATCHED"
    }
  },
  "context": {
    "inputs": {
      "discount_percent": 10
    }
  }
}

mode: "rulebook" does not call an LLM. It validates the request rulebook against the published JSON Schema, hashes the rulebook, evaluates bounded conditions, and returns yes, no, or review alongside the application verdict, action, reason code, matched rule, and evaluator_version. Responses also include rulebook_contract with the enforced schema URL/hash, runtime_binding with the direct or trusted-adapter binding mode, input_hash, a SHA-256 hash of the canonical inputs or adapter facts consumed by the declarative evaluator, plus a rulebook_attestation_v1 bundle hash over the deterministic execution tuple. Production deployments can sign that bundle hash with a rulebook_attestation_signature_v1 Ed25519 envelope; verification keys are published at /.well-known/rulebook-attestation-keys.json. Set DECIDE_RULEBOOK_ATTESTATION_SIGNATURE_REQUIRED=true in production to fail closed instead of returning unsigned Rulebook decisions. Publish retired public verification keys with DECIDE_RULEBOOK_ATTESTATION_KEY_HISTORY_JSON so older Decision Records remain verifiable after rotation.

Rulebook requests cannot preload Decide-generated Decision Record material. Fields such as runtime_binding, trusted_adapter, adapter_facts, rulebook_attestation, application_verdict, and action are response-only at the request body, context.inputs, and adapter-facts boundaries; attempts return RULEBOOK_OUTPUT_MATERIAL_FORBIDDEN.

Legacy single, multi, and runtime requests remain available for AI-assisted exploration, but they are not binding production verdicts. Those responses include decision_contract with authority: "advisory_only" and production_verdict: false, plus production_binding_required: true and the supported production binding modes; callers that need deterministic execution must use mode: "rulebook" and capture rulebook_contract, runtime_binding, and the Rulebook attestation material.

At the public Decision Record boundary, successful evaluations are registered as immutable tenant-scoped snapshots. Historical replay restores the original canonical input and stored rulebook snapshot rather than trusting a caller override or the current application deployment.

Rulebook v1 also supports registered first-party trusted adapters for bounded fact normalization. Adapter requests pin an exact semantic version and manifest hash; responses attest the bundled implementation source hash plus canonical input/output hashes and the enforced execution contract. Each invocation runs once in an empty-environment worker with hard time/resource limits and denied common ambient capabilities. The declarative rulebook remains the only binding verdict selector. See docs/TRUSTED_ADAPTERS_V1.md.

The current reference applications prove both production patterns: Solana Execution Gate, Decision Memo Readiness Gate, and Krafthaus Workflow Readiness Binding use trusted adapters before Rulebook v1, while the Refund, Trial, Cancel, and Return Policy MCP notaries supply normalized facts directly to Rulebook v1 and expose the signed rulebook result through their stable REST and MCP surfaces.

Before evaluator, adapter, or rulebook changes ship, run the local historical replay gate:

npm run rulebook:migration-dry-run -- --json

Use --candidate-rulebook, --candidate-adapter, and --candidate-evaluator-version to compare proposed migrations against the golden replay corpus before production routing changes.

For release gates, prefer a rulebook_migration_v1 manifest so candidate artifacts, expected drift, and approval status are reviewed together:

npm run rulebook:migration-dry-run -- --migration path/to/migration.json --json

The manifest schema is published at https://api.decide.fyi/schemas/rulebook-migration-v1.schema.json, and the dry run validates manifests against that closed schema before replay.

After production routing or runtime-contract changes ship, run the production runtime smoke:

npm run smoke:rulebook-runtime

This hits https://api.decide.fyi from outside the runtime and verifies the published hybrid_declarative_rulebook_with_trusted_adapters manifest, closed Rulebook v1 schema, attestation key endpoint, direct declarative evaluation, executable-rulebook rejection, and advisory-only contract metadata on legacy AI-assisted responses. GitHub Actions also runs this as the scheduled/manual Rulebook Runtime Production Smoke workflow.

The legacy single, multi, and runtime modes are AI-assisted surfaces. They are not the production determinism boundary for loosely defined business judgment.

Architecture:

• Ecosystem constitution
• Application binding contract
• Rulebook v1 contract
• Rulebook compatibility policy
• Rulebook migration examples
• Rulebook migration manifest

One-Click Install

Buttons install the Refund Notary server. To add all 4 servers, use the JSON config below.

Stable MCP Remotes

All servers: 100 vendors, US region, individual plans, stateless, no auth, 100 req/min. Runtime contracts and reference evidence stay here.

Quick Start

Connect via MCP (Claude Desktop / Windsurf / other clients)

{
  "mcpServers": {
    "refund-decide": { "url": "https://refund.decide.fyi/api/mcp" },
    "cancel-decide": { "url": "https://cancel.decide.fyi/api/mcp" },
    "return-decide": { "url": "https://return.decide.fyi/api/mcp" },
    "trial-decide":  { "url": "https://trial.decide.fyi/api/mcp" }
  }
}

REST API

# Refund eligibility
curl -X POST https://refund.decide.fyi/api/v1/refund/eligibility \
  -H "Content-Type: application/json" \
  -d '{"vendor":"adobe","days_since_purchase":12,"region":"US","plan":"individual"}'

# Cancellation penalty
curl -X POST https://cancel.decide.fyi/api/v1/cancel/penalty \
  -H "Content-Type: application/json" \
  -d '{"vendor":"adobe","region":"US","plan":"individual"}'

# Return eligibility
curl -X POST https://return.decide.fyi/api/v1/return/eligibility \
  -H "Content-Type: application/json" \
  -d '{"vendor":"adobe","days_since_purchase":12,"region":"US","plan":"individual"}'

# Trial terms
curl -X POST https://trial.decide.fyi/api/v1/trial/terms \
  -H "Content-Type: application/json" \
  -d '{"vendor":"adobe","region":"US","plan":"individual"}'

Local Dev Checks

Start local dev server:

npx vercel dev

In a separate terminal:

# Handler-level smoke checks (no running server required)
npm run smoke

# MCP endpoint checks (requires a running server)
npm run mcp:check

# Self-contained local MCP check; starts/stops vercel dev on localhost:3000
npm run mcp:check:local

# End-to-end workflow fixture (example -> result)
npm run workflow:test

# Production customer-key verification after provisioning a key
DECIDE_SMOKE_API_KEY='<customer-key>' npm run smoke:customer-key

Zendesk Workflow Orchestrators

Use workflow endpoints when you want one request to return:

• decision classification (yes | no) from /api/decide
• policy result from the relevant notary endpoint
• recommended Zendesk action + tags + private note with request_id

Endpoints

• POST https://refund.decide.fyi/api/v1/workflows/zendesk/refund
• POST https://cancel.decide.fyi/api/v1/workflows/zendesk/cancel
• POST https://return.decide.fyi/api/v1/workflows/zendesk/return
• POST https://trial.decide.fyi/api/v1/workflows/zendesk/trial

Request

{
  "ticket_id": "ZD-9001",
  "workflow_type": "refund",
  "question": "Should this Adobe annual plan refund request proceed under policy?",
  "vendor": "adobe",
  "region": "US",
  "plan": "individual",
  "days_since_purchase": 5
}

For refund and return, include days_since_purchase.

Deterministic test mode

Set decision_override to bypass model classification during fixtures and CI:

{
  "decision_override": "yes"
}

Response (example)

{
  "ok": true,
  "flow": "zendesk_refund_v1",
  "ticket_id": "ZD-9001",
  "decision": { "c": "yes", "request_id": "req_123" },
  "policy": { "verdict": "ALLOWED", "code": "WITHIN_WINDOW" },
  "action": {
    "type": "approve_refund",
    "zendesk_tags": ["decide", "decide_yes", "refund_allowed"]
  }
}

Refund Notary

Endpoint: POST https://refund.decide.fyi/api/v1/refund/eligibility MCP Tool: refund_eligibility

Checks if a subscription purchase is within the vendor's refund window.

Input: vendor, days_since_purchase, region, plan

{"refundable":true,"verdict":"ALLOWED","code":"WITHIN_WINDOW","message":"Refund is allowed. Purchase is 12 day(s) old, within 14 day window.","vendor":"adobe","window_days":14}

Codes: WITHIN_WINDOW, OUTSIDE_WINDOW, NO_REFUNDS, UNSUPPORTED_VENDOR

Cancel Notary

Endpoint: POST https://cancel.decide.fyi/api/v1/cancel/penalty MCP Tool: cancellation_penalty

Checks cancellation penalties — early termination fees, contract locks, or free cancellation.

Input: vendor, region, plan

{"verdict":"PENALTY","code":"EARLY_TERMINATION_FEE","message":"adobe charges an early termination fee: 50% of remaining months on annual plan.","vendor":"adobe","policy":"etf"}

Codes: NO_PENALTY, EARLY_TERMINATION_FEE, CONTRACT_LOCKED, UNSUPPORTED_VENDOR

Return Notary

Endpoint: POST https://return.decide.fyi/api/v1/return/eligibility MCP Tool: return_eligibility

Checks if a subscription purchase can be returned/reversed, with return type and method.

Input: vendor, days_since_purchase, region, plan

{"returnable":true,"verdict":"RETURNABLE","code":"FULL_RETURN","message":"Return is available. Purchase is 5 day(s) old, within 14-day window.","vendor":"adobe","return_type":"full_refund","method":"self_service"}

Codes: FULL_RETURN, PRORATED_RETURN, CREDIT_RETURN, OUTSIDE_WINDOW, NO_RETURNS, UNSUPPORTED_VENDOR

Trial Notary

Endpoint: POST https://trial.decide.fyi/api/v1/trial/terms MCP Tool: trial_terms

Checks free trial availability, length, card requirement, and auto-conversion status.

Input: vendor, region, plan

{"verdict":"TRIAL_AVAILABLE","code":"AUTO_CONVERTS","message":"adobe offers a 7-day free trial. Credit card required. Auto-converts to paid plan.","vendor":"adobe","trial_days":7,"card_required":true,"auto_converts":true}

Codes: AUTO_CONVERTS, NO_AUTO_CONVERT, TRIAL_NOT_AVAILABLE, UNSUPPORTED_VENDOR

Supported Vendors (100)

Scope: US region, individual plans only.

Data Freshness

Policies are sourced from official vendor documentation and terms of service.

• Daily automated checks — GitHub Action runs at 08:00 UTC, hashing vendor policy pages across all 4 services (refund, cancel, return, trial). If a page changes, an issue is opened for review.
• Policy source URLs tracked — Each service has its own sources file in rules/ linking to official policy pages.
• Compliance export — GET /api/compliance-export returns a CSV snapshot of tracked sources, hashes, and pending candidate changes (?format=json for machine-readable output).
• Versioned rules — Each rules file includes a rules_version field for staleness detection.

Architecture

• Stateless — No database, no sessions, no side effects
• Deterministic — Same input always produces same output
• Versioned Rules — Rules files include version for tracking changes
• Daily Monitoring — GitHub Action checks all vendor policy pages daily
• Serverless — Runs on Vercel serverless functions
• Zero Dependencies — Core compute logic has no external dependencies
• Hostname Routing — Vercel middleware routes subdomains to correct MCP endpoints

Limitations

• US Only — Currently only supports US region
• Individual Plans Only — Business/enterprise plans not yet supported
• Calendar Days — Windows are based on calendar days, not business days
• Static Rules — Does not account for promotional offers or special circumstances

Changelog

Unreleased

Added:

• GET /api/compliance-export endpoint for policy monitoring evidence export (CSV default, JSON via ?format=json).
• Smoke test coverage for compliance export JSON and CSV paths.

Changed:

• Landing pages now position Decide as the Decision API engine and frame Policy MCP Notaries as one reference application.

v1.2.1 (2026-02-08)

Changed:

• Subdomain homepage now shows the relevant notary card (refund/cancel/return/trial).
• Version metadata is consistent across server.json, MCP initialize, and /.well-known/*.

v1.2.0 (2026-02-02)

Added:

• Cancel Notary MCP (cancel.decide.fyi) — cancellation penalty checker
• Return Notary MCP (return.decide.fyi) — return eligibility checker
• Trial Notary MCP (trial.decide.fyi) — free trial terms checker
• Hostname-based middleware routing for all subdomains
• Policy source files and daily checking for cancel, return, and trial policies
• Systems/Agents mode framing on landing page
• MCP catalog with cards for all 4 servers

Fixed:

• Daily policy checker: added contents:write permission and fixed shell logic
• Removed dead Cloudflare email-decode scripts causing 404s

v1.1.0 (2026-02-01)

Added:

• Expanded from 64 to 100 supported vendors
• Daily policy-check GitHub Action (cron at 08:00 UTC)
• Policy source URLs tracked in rules/policy-sources.json
• MCP vendor enum in inputSchema for agent discoverability

Fixed:

• ERR_IMPORT_ATTRIBUTE_MISSING crash on Vercel (Node 22 import attributes)

v1.0.0 (2026-01-15)

Added:

• Initial release with REST API and MCP server
• Support for 9 vendors

Free API (Default: No Auth)

All 4 policy servers are free to use. No authentication. No API keys.

/api/decide is public by default, and can be protected by setting DECIDE_API_KEY in server env vars.

If you run decide behind the decidesite proxy with dynamic customer keys, also set:

• DECIDE_PROXY_SHARED_TOKEN: shared secret required in x-decide-proxy-token header for trusted proxy calls.
• DECIDE_API_KEY: backend internal key that the trusted proxy forwards upstream (recommended to keep backend private).

Rate limit: 100 requests/minute per IP.

For first-customer handoff and keyed production verification, see docs/FIRST_CUSTOMER_RUNBOOK.md.

Policy Fetch Hook (for policy checker browser-hook lane)

Use POST /api/policy-fetch-hook as a fetch adapter for the daily checker when direct fetches are blocked.

Request body:

{
  "url": "https://example.com/policy",
  "vendor": "example_vendor",
  "policy_type": "refund",
  "timeout_ms": 18000
}

Auth:

• Authorization: Bearer <POLICY_CHECK_BROWSER_HOOK_TOKEN> or x-hook-token: <token>

Server env:

• POLICY_CHECK_BROWSER_HOOK_TOKEN (required for endpoint auth)
• POLICY_FETCH_BROWSERLESS_TOKEN (optional; enables browserless render first)
• POLICY_FETCH_BROWSERLESS_CONTENT_URL (optional override; default https://chrome.browserless.io/content)
• POLICY_FETCH_ALLOWED_HOSTS (optional comma-separated host allowlist)

Checker (GitHub Actions, repo decide):

• Secret POLICY_CHECK_BROWSER_HOOK_URL = deployed endpoint URL (example: https://decide-1.vercel.app/api/policy-fetch-hook)
• Secret POLICY_CHECK_BROWSER_HOOK_TOKEN = same token as runtime env
• Variable POLICY_CHECK_FETCH_LANES_DEFAULT = browser_hook,direct,zendesk_api,mirror

Questions? support@decide.fyi or @decidefyi on X

Links

• Website: https://decide.fyi
• Policy alerts: https://www.decide.fyi/resources/policy-alerts
• Refund: https://refund.decide.fyi
• Cancel: https://cancel.decide.fyi
• Return: https://return.decide.fyi
• Trial: https://trial.decide.fyi
• X/Twitter: @decidefyi
• MCP Spec: https://modelcontextprotocol.io

Decide is the API engine. Applications prove the primitive.