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

Annotations already declare it is a non-read-only but non-destructive, open-world operation; the description adds material context beyond that: a 50-credit cost, asynchronous execution, and the single-face precondition that causes failures. It does not cover failure modes beyond the face constraint or credit-refund behavior, keeping it below 5.

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 short sentences, zero filler, with the core action and input constraint front-loaded and cost plus async follow-up in the second sentence.

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?

An output schema exists, so return values needn't be detailed, yet the description still flags the project id and the wait_for_image_project follow-up, plus cost and the async model. Complete enough to invoke correctly; only failure/error handling is unaddressed.

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 coverage is 67%, so most parameter meaning already comes from structured fields. The description reinforces the one-face requirement on assets and gestures at 'optional appearance instructions' (the style.prompt object) but doesn't name parameters or clarify the default naming behavior, adding only marginal value over the schema.

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?

States a specific verb and resource ('Creates a headshot') plus the key input constraint ('from a supplied photo containing one detectable face') and the optional style customization. That distinguishes it from generic siblings like generate_image or edit_image without naming them, so it stops just short of a 5.

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?

Gives clear context for use plus a concrete routing instruction: it starts a background job and returns a project id 'for wait_for_image_project', which tells the agent exactly which sibling to chain. It does not say when to prefer a sibling such as swap_head_in_photo or edit_face_in_photo instead, so no explicit exclusions.

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