Decision API engine

decide.fyi is the Decision API engine.

Stable runtime endpoints for deterministic system and agent decisions. Reference applications show the same contract powering policy MCPs, decision memo packets, and execution gates.

Core runtime

Use Decide when your system needs deterministic verdicts, request IDs, and repeatable decision logic.

REST
POST /api/v1/{policy}/{action}
Output
ALLOWED | DENIED | UNKNOWN or policy-specific verdicts
Role
Infrastructure layer, not the human-facing product suite.
Engine stays here

Reference applications

Policy MCPs, decision memo packets, and execution gates prove the same narrow contract: deterministic verdict, request ID, replayable evidence.

Applications prove the primitive

Stable notary remotes

Refund Notary

Stable runtime endpoint for policy-check reference applications.

MCP
refund.decide.fyi/api/mcp
REST
POST /api/v1/refund/eligibility

Cancel Notary

Stable runtime endpoint for policy-check reference applications.

MCP
cancel.decide.fyi/api/mcp
REST
POST /api/v1/cancel/penalty

Return Notary

Stable runtime endpoint for policy-check reference applications.

MCP
return.decide.fyi/api/mcp
REST
POST /api/v1/return/eligibility

Trial Notary

Stable runtime endpoint for policy-check reference applications.

MCP
trial.decide.fyi/api/mcp
REST
POST /api/v1/trial/terms
Compatibility promise

Existing MCP registry links, GitHub notary lists, and client configs can keep using Decide URLs. Applications can build policy MCPs, memo packets, and execution gates on the same contract.

MCP server card Runtime GitHub Agent card