# REL03-BP03: Provide service contracts per API

## Description

Define và maintain API contracts giữa services.

## Implementation Guidance

- Use OpenAPI/Swagger for REST APIs
- Implement contract testing
- Version APIs appropriately
- Document breaking vs non-breaking changes
- Use schema validation

## Risk Level

High - Broken contracts cause cascading failures.

## Related Best Practices

- [REL03-BP02](REL03-BP02-Domain-Focused-Services.md)
- [REL05-BP01](../REL05-Workload-Mitigate-Failures/REL05-BP01-Graceful-Degradation.md)
