# description
Frontmatter shape for nodes classified as `hook`. Extends `base.schema.json`. Kind-specific fields: `event`, `condition`, `blocking`, `idempotent`.

# properties.event.description
Event name this hook reacts to (e.g. `PreToolUse`, `PostToolUse`, `SubagentStop`, `SessionStart`). Platform-specific enum; adapters MAY validate.

# properties.condition.description
Free-form predicate expression evaluated by the host. Syntax is platform-specific; the spec does not constrain it.

# properties.blocking.description
When true, the host MUST wait for the hook to finish before proceeding. When false, the hook runs fire-and-forget.

# properties.idempotent.description
Author-declared: executing twice with the same inputs produces the same result. Consumed by runners for retry and dedup.