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

Annotations are all false (readOnlyHint, openWorldHint, idempotentHint, destructiveHint), so the description carries the full burden. It discloses cost ('FREE'), side effects ('renders nothing'), and critically explains the consent semantics: 'never assert that on their behalf.' It also clarifies the source field's meaning and warns against using 'upload'/'social' for non-real people. This exceeds what annotations provide and is highly transparent.

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?

The description is a single dense paragraph, but it is well-organized: it starts with the core purpose, then input instructions, then a clear 'LIKENESS' section. Every sentence contributes new information (cost, side effects, source semantics, consent). It is not verbose or redundant, though it is long. The structure front-loads the primary use case, making it easy to parse.

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?

Given the tool's complexity (7 parameters, no output schema) and minimal annotation coverage, the description is remarkably complete. It covers the main workflow, input requirements (public url, name), reuse via list_creators and generate functions, the distinction between generated and real people, and the critical consent requirement. There's no output schema, so return value explanation isn't needed. It leaves no essential gap for an agent to call it correctly.

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?

With 100% schema description coverage, the baseline is 3, but the description adds substantial meaning beyond the schema. For 'image', it clarifies a public https url is required and specifically warns 'Not a local file path — upload it with upload_file first'. For 'source', it explains what each enum value means in practice. For 'consented', it states 'never assert that on their behalf'. These annotations elevate the parameter guidance beyond dry field descriptions.

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 opens with a specific verb and resource: 'Add a portrait to this workspace’s reusable CAST' and explains the outcome ('the SAME person can star in future ads'). It differentiates from sibling tools like list_creators and delete_creator by describing the exact action and its effect, and even references the app's UI equivalent ('the headless twin of the app’s ＋ ▸ Pick a creator ▸ save'). This is unambiguous and distinct.

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?

The description clearly implies when to use: when you want to make a person reusable across ads. It explains the inputs (public url + name) and the consequences (list_creators returns them, urls can be reused). It also gives a strong behavioral cue by stating 'Saving is FREE and renders nothing', which helps decide whether to call it. However, it does not explicitly state when NOT to use it or name direct alternatives beyond the app equivalent, so it stops short of a 5.

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