Preview the records that would be ingested for the given source payload, without persisting anything. Use this to validate filters / list selections before committing to Create.

Per-source body shapes and field semantics live in /docs/source-detail/{source_id}.txt. The route schema only enforces that the body is a JSON object; per-source validation runs inside the handler and surfaces as 400 with a specific message and, when multiple fields fail, an errors[] array of {field, message} entries.

Results are typically capped at 100 rows (source-specific — e.g. Slack returns up to 10). metadata.total_results is the count returned in this preview; it is omitted when the source cannot count the matches. When metadata.capped is true, more rows exist upstream but were omitted due to preview limits.

Trimming the response. Pass a top-level limit (positive integer) to cap how many rows come back — useful when you only need to eyeball the shape of a row rather than the whole sample. limit is a response-shaping knob applied by this endpoint: it does not reduce what the source fetches upstream, and it never changes metadata.total_results. When it drops rows, metadata.capped is true.

{
  "limit": 3
}