attac-t Skill: Events
"Events are for side effects. Actions are for intent."
The Decision
Use Events when:
- Side effects can multiply (notifications, logs, syncs)
- Consumers don't need the result
- Cross-domain communication is needed
- The trigger shouldn't know about all consequences
Use Direct Calls when:
- The caller needs a return value
- There's exactly one consumer, forever
- Failure must halt the operation
The Heuristic
Ask: "If I add another consequence later, should the caller change?"
- No → Event
- Yes → Direct call
The Quick Test
| Ask Yourself | Answer | Use |
|---|---|---|
| Multiple reactions possible? | Yes | Event |
| Caller needs result? | Yes | Direct |
| External system involved? | Yes | Event |
| Single, obvious dependency? | Yes | Direct |
Real-World Examples
For concrete examples, see examples.md.