402 Frameworks Quarkus REST Agent Skill

Quarkus REST API Guidelines

Apply REST API design principles on Quarkus using Jakarta REST (JAX-RS).

What is covered in this Skill?

• Resource classes, @Path, HTTP method mapping, and resource URI design
• Status codes, Location headers, and Response building
• DTOs and Bean Validation at the boundary; ISO-8601 for date/time fields
• ExceptionMapper for consistent error JSON (RFC 7807 Problem Details)
• API versioning strategies (URI path, Accept header)
• Idempotency with Idempotency-Key header
• Optimistic concurrency: ETag, If-Match, If-None-Match
• HTTP caching with Cache-Control headers
• API deprecation: Sunset and Deprecation headers
• Pagination, sorting, and filtering query parameters
• Optional /openapi via SmallRye; API-first contract maintained in openapi.yaml (codegen)
• Reactive vs blocking considerations; @RunOnVirtualThread
• Security integration at the filter layer

Scope: Apply recommendations based on the reference rules and good/bad code examples.

Constraints

Before applying REST changes, ensure the project compiles. After applying improvements, run full verification.

• MANDATORY: Run ./mvnw compile or mvn compile before applying any change
• PREREQUISITE: Project must compile before applying REST API improvements
• SAFETY: If compilation fails, stop immediately
• BLOCKING CONDITION: Compilation errors must be resolved by the user before proceeding
• VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
• BEFORE APPLYING: Read the reference for detailed rules and examples

When to use this skill

• Review or improve JAX-RS resources in a Quarkus project
• Design HTTP APIs with validation and error handling on Quarkus
• Add API versioning, idempotency, ETag concurrency, or deprecation headers
• Implement pagination, sorting, or RFC 7807 Problem Details error responses
• Improve Quarkus REST resources and exception mappers

Workflow

• Read reference and assess project context

Read references/402-frameworks-quarkus-rest.md and inspect the current project setup before proposing changes.

• Gather scope and decide target improvements

Identify requested outcomes, constraints, and the minimum safe set of changes to apply.

• Apply framework-aligned changes

Implement or refactor configuration/code following the reference patterns and project conventions.

• Run verification and report results

Execute appropriate build/tests and summarize what changed, what was verified, and any follow-up actions.

Reference

For detailed guidance, examples, and constraints, see references/402-frameworks-quarkus-rest.md.