Event Source Dry Run

Preview an event source without any side effects — fetch, diff against the last value, and evaluate the condition, but never publish, run an action, or advance the cursor. Returns the sampled value, whether it changed, the would-emit event, and whether the condition would pass. The preview the /wb-event-new authoring loop shows before activating.

MCP name: event_source_dry_run

Category: events

Parameters

Name	Type	Required	Description
name	str	No	The event source name (the .md file stem). Provide this to preview a saved source.
proposal	dict	No	The structured event_source_create fields (name, source_type, interval, extract_*, condition, action, semantic, ...), to preview a not-yet-saved source — what /wb-event-new's dry-run step passes. Provide either name or proposal.
run_semantic	bool	No	If true, actually evaluate the Tier-3 semantic gate (a real web search + local-model call). Default false — the semantic block is only reported (semantic_pending), keeping the preview cheap and side-effect-free.

Details

Run a single source poll with zero side effects: fetch the payload, extract the watched value, diff it against the stored cursor, and — if it changed — evaluate the source's CEL condition over the would-emit event. Nothing is published, no action runs, and the cursor is not advanced, so this is safe to call repeatedly while authoring. Returns {changed, current, prev, would_emit, condition_passed, would_fire} so the author can see exactly what would happen before activating the source.