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

While annotations already declare readOnlyHint and idempotentHint, the description adds significant behavioral context: avatars are generated by Genpio's proprietary model (not third-party), there is no per-avatar metadata, and private clones are excluded. These details go beyond the annotations and clarify scope and limitations.

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 three sentences long, front-loaded with the primary purpose in the first sentence, followed by two sentences of relevant context. Every sentence earns its place without redundancy or fluff.

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 simplicity (one optional parameter, no output schema), the description provides a complete picture: what is returned (count, ids, URL template), the proprietary nature, the lack of filtering, and the exclusion of private avatars. This is sufficient for an agent to decide whether to use the tool and what to expect.

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?

The schema already fully documents the single 'limit' parameter with a clear description. The tool description does not add any additional meaning about the parameter itself, but the schema coverage is 100%, so the baseline of 3 is appropriate.

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 clearly states the tool's function: report how many public avatars Genpio publishes, return their ids, and provide the URL template for portraits. This is a specific verb+resource+output, and the mention of 'public avatars' and 'private clones never listed' distinguishes it from sibling tools like list_voices or list_open_roles.

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 provides clear context for when to use this tool, including explicit exclusions: it cannot filter by name, gender, or nationality because no per-avatar metadata exists, and private customer avatar clones are never listed. However, it does not explicitly name alternative tools for those cases, so it stops short of full when/when-not guidance with named alternatives.

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