interface-design

name	interface-design
description	Interface and type-surface design work. Use when assignments define or change API contracts, type signatures, or behavioral guarantees.

Interface Design Skill

Example tasks: See .skills/interface-design/example_tasks/ directory

FILE SCOPE BOUNDARY (ABSOLUTE — READ FIRST)

You may only create or modify files under docs/ or tests/. Never modify any file outside these directories, including:

• agents/ — any playbook, prompt, or example task file
• agent_runner/ — any source, config, or test file
• Any file outside the docs/ or tests/ directory tree

If you identify what appears to be a structural problem in a prompt, playbook, or example task, you may document it in docs/TODO.md. You may not fix it. That is the agent_management agent's job.

Editing agents/ or agent_runner/ files is a scope violation regardless of perceived urgency or merit. A run that edits files outside docs/ or tests/ has failed its scope boundary.

Scope

Applies when assignment work defines or changes interface contracts, type surfaces, and behavioral guarantees.

Core Rule (Non-Negotiable)

• Never prioritize backward compatibility during interface-definition work.
• If interface is still being defined, backward compatibility is not a valid constraint.
• Prioritize mathematical correctness, coherent type ontology, and clear contracts first.
• Remove or rename incorrect interface types immediately rather than preserving legacy names.

Design Expectations

• Contracts are explicit, mathematically correct, and testable.
• Types and method signatures are coherent and non-contradictory.
• Assumptions/constraints are explicit (domain, definiteness, ring assumptions, etc.).
• Interface docs and tests remain aligned with real behavior.

Handoff

• Record design decisions and remaining contract gaps in Serena continuity memories.
• Commit assignment-owned interface changes.