Custom ROS 2 Interfaces

Source: ros2-copilot-skills custom interfaces skill

Why This Matters

Interface design is where a robot project either becomes coherent or drifts into topic-name folklore. Custom messages, services, and actions are not just transport schemas. They are the public contracts that let subsystems evolve without constant archaeological debugging.

Distilled Takeaways

• Keep interfaces in dedicated interface packages to avoid circular dependency pain.
• Design fields for operational meaning, not just for what is easiest to publish right now.
• Constants and explicit naming conventions can make status and mode messages far easier to consume safely.
• Interface changes ripple across builds, generated code, and runtime expectations, so treat them as deliberate versioned changes.
• A good action or service definition usually starts with a good message vocabulary.

Practical Guidance

• Use standard messages when they already express the concept well.
• Create custom interfaces when the robot genuinely has a reusable domain API.
• Keep request, result, and feedback semantics crisp so higher-level autonomy can reason about them.
• Rebuild and re-source immediately after interface edits. Anything else invites ghost bugs.

Corroborating References

• ROS 2 custom interface tutorial
• ROS 2 actions tutorial

When to Read the Original Source

Go to the original skill when you want example package structure, CMake and package.xml snippets, field-type reminders, and the explicit warnings around dependency declarations and interface-package layout.