A mutation entry is not an object

artf.mutation.not_objecterrorARTF mutation set

An entry in the mutations array is not a Mutation object, so it carries no intent, operation, or path to check.

What it means

One member of the mutations array is a scalar or an array rather than an object. Each entry is a Mutation message with intent, op, path, and one value payload.

Why it matters

It is usually a list of ids where a list of mutations belongs, which means the agent's builder collapsed one nesting level and every mutation in that batch is lost.

How to fix it

Wrap each proposed change in a Mutation object, even when the change is a single id.

Example that trips it

{ "id": "ep-1", "mutations": ["deal-2"], "metadata": { "api_version": "1.0.0" } }

Check your payload

Paste a bid request or response into the tester to see whether this code fires against it, or gate on the id in CI with the CLI: the id is stable, wording is not.

Back to the full diagnostic code reference.