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

Adds substantial behavior beyond the annotations: the call finishes synchronously, credits are only charged when a portrait returns (billing semantics), defect checking on hands/face/background, and full auth requirements (OAuth or Bearer API key). Annotations only cover the safety profile (non-readonly, idempotent, non-destructive).

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?

Front-loads the core purpose and the prerequisite quote_id before the billing and auth details. Dense but every clause carries distinct value (defect check, billing trigger, auth options); the auth sentence is long but necessary.

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 generation tool with an output schema and full annotation coverage, the description supplies the missing pieces: prerequisite tool, billing trigger, and auth setup. Nothing an agent needs to invoke it correctly is absent.

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 the baseline is 3, but the description adds a cross-tool constraint the schema doesn't: quote_id must originate from estimate_ad_cost with kind "avatar". Other params (prompt, save_as, aspect_ratio) are already well documented in 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 (Generate) and resource (creator portrait / avatar) with clear downstream usage ('to use as the avatar in generate_ad'), distinguishing it from siblings like generate_image and generate_ugc_video. An agent can identify its role without opening the schema.

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: it's the avatar source for generate_ad and requires a quote_id from estimate_ad_cost with kind "avatar", effectively naming the prerequisite step. It stops short of explicitly stating when to prefer this over generate_image, but the workflow routing is strong.

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