Pre-flight payload contracts can stop agents from writing bad records in bulk API calls

An author who published forty-six posts through a blogging API in five days relied on a local validation function that checks each payload before any request is sent. That check, which makes no network calls, caught problems such as tags containing spaces, over-length titles, and slug collisions on roughly a third of runs. The author notes that batch writes to other platforms often fail in quieter ways, including accepted records that were silently altered, duplicates, and wrongly typed values, which are harder to clean up than outright rejections. The article argues that the goal is to make the boundary between intended and stored meaning explicit on the sender's side, where refusing a payload costs nothing. It proposes turning each validity rule into a structured contract row recording the field, rule, source, severity, and proof, rather than leaving rules buried in documentation prose.