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

Annotations cover the safety profile (non-destructive, idempotent, open-world), and the description adds substantial context beyond them: credits are charged only on success, the call returns an id to poll, an explicit image_rights_consent requirement, and full auth instructions (OAuth or Bearer acd_live_ key with URL). This is genuinely rich behavioral disclosure.

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-loaded with the core action and modes, then prerequisites, then cost/polling behavior. The trailing SIGN-IN block is dense but earns its place for an auth-required tool; overall efficient though slightly long.

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 complex, authorized, credit-charged generation tool, the description covers inputs' provenance, consent gating, cost timing, async polling, and authentication. Since an output schema exists, no return-shape detail is needed, and nothing an agent needs to invoke it correctly is missing.

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 cross-tool meaning: it names where template comes from (list_ugc_avatars) and where quote_id comes from (estimate_ad_cost with kind "ugc"), clarifying the authoring flow 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?

States a specific verb+resource ('Make a UGC-style creator video') and clearly delineates the two modes (catalogue creator via template vs. person's own photo via image_url), distinguishing it from generic siblings like generate_video and generate_avatar.

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 prerequisites and routes the agent to sibling tools: template 'from list_ugc_avatars', quote_id 'from estimate_ad_cost with kind "ugc"', and polling via get_generation. It implies when to use it (UGC creator content) but doesn't explicitly state when to choose generate_video or generate_avatar instead.

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