A real trigger_payload for manually testing an event_integration_webhook trigger, built from Nango's currently-synced records — same shape a live webhook delivery produces. The Builder UI calls this before POST /{workflow_id}/run so "Run now" exercises the workflow with real data instead of an empty {} that only fails once some downstream node templates into {{trigger.record...}}. Same role check as /run — anyone who can start a run can preview its payload.

404 (not 422) when there's nothing to test with yet: this is a "no data" condition, not a malformed request — the workflow itself may be perfectly valid and simply have no matching synced record right now.