Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (which only confirm it is a non-destructive write with open-world scope), the description discloses two critical traits: the operation costs 10 credits and it is asynchronous, returning a project id that must be polled via wait_for_image_project. The content-policy constraints add further behavioral context the annotations do not carry.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight paragraphs: the safety/authorization constraint is front-loaded, then the mechanics (swap, cost, return value). Every sentence carries information; no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an async, credit-consuming image mutation tool, the description covers purpose, cost, required follow-up workflow, and usage restrictions, while the input schema fully documents parameters and an output schema exists to describe return values. Nothing an agent needs in order to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, and each of the three parameters (name, nested assets paths, max_resolution) is fully documented in the schema with examples and format rules. The description adds no parameter-level meaning, which is acceptable given the schema does the heavy lifting, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a concrete verb and resource: it 'swaps a head from a supplied image onto a supplied body image', which is clearly more specific than the title. It does not explicitly distinguish itself from close siblings such as swap_face_in_photo, edit_face_in_photo, or place_person_in_scene, so an agent must infer the head-vs-face distinction.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It states clear when-not conditions ('Do not use for impersonation, deception, sexual content, or content involving minors') and a required authorization precondition regarding likeness rights. It also directs the agent to the follow-up call ('returns a project id for wait_for_image_project'), though it never names a sibling alternative for face-level edits.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.