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

With no annotations, the description carries the full burden; it does disclose two genuinely useful facts the schema cannot: a credit cost of 3 and the return shape { processedImage }. However, it is silent on processing latency, whether uploaded faces are stored or retained, and failure modes for non-face inputs, which matters for a tool that takes personal biometric imagery.

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?

Three short sentences: purpose first, return value second, cost last. Every clause carries information an agent would otherwise have to guess, and nothing is repeated from the schema.

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 a simple two-parameter generation tool with no output schema, the description covers purpose, return key, and cost, which is enough to select and invoke it. The remaining gap is that it never mentions where the resulting image goes (e.g., saved to the user's artworks, as sibling tools like list_my_artworks imply), which could affect follow-up calls.

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 100%, so both the image format (base64 data URI or HTTPS URL) and the eight-value style enum with its pixar default are already fully documented. The description adds only the loose notion of a "stylized avatar" and does not clarify style trade-offs or image requirements beyond what the schema states.

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?

Names a specific verb and resource ("Generate a stylized avatar from a face photo") and scopes the input to a face photo, which implicitly separates it from generic image tools like create_image or ai_filters. It does not explicitly name a sibling such as headshot_generator or cartoonize, so the differentiation is inferable rather than stated.

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 phrase "from a face photo" implies the appropriate input context, but there is no explicit when-to-use guidance versus headshot_generator, portrait_retouch, or cartoonize, and no stated preconditions or exclusions.

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