API Contract First

The Law

NO API IMPLEMENTATION WITHOUT A REVIEWED CONTRACT.
Writing endpoints before the contract is building to a spec that doesn't exist.
The contract IS the spec. Code that matches it is correct. Code that doesn't is wrong.

When to Use

Use this skill before writing ANY of these:

• A new REST endpoint
• A new gRPC/protobuf service method
• A new GraphQL query, mutation, or subscription
• A new event schema (Kafka, SQS, webhooks)
• A new inter-service interface