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

With only openWorldHint in annotations, the description adds substantial behavior: it waits 1–5 minutes, returns a preview, charges 60 credits per motion with idle free, and explains how clips versus rebuild work. It also notes that realistic style animates as video and breathes free immediately. It does not cover failure handling, cancellation, or auth requirements, so it is strong but not exhaustive.

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 front-loads the core choice between new design and existing image, but it is a dense paragraph with nested parentheses, semicolons, and quoted engine names. The information is useful, yet the structure makes it harder to parse than necessary. It is concise in length but not well organized.

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?

The description covers the main creation modes, costs, wait time, and preview return, which is important for a tool with no output schema. However, it does not explain what the preview contains, whether a job ID is returned, how to retrieve the final asset, or what happens if both prompt and image_url are supplied. Given the tool's complexity and minimal annotations, these are meaningful gaps.

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 schema already documents all six parameters. The description still adds meaning beyond the schema by explaining prompt versus image_url, the consequence of engine clips versus rebuild, and the realistic style exception. It does not add much for notes or max_credits beyond what the schema already says.

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 states a specific verb and resource: design a new mascot from a prompt or bring an existing mascot image. It also distinguishes the two engines, clips versus rebuild, and the special realistic style. It does not explicitly differentiate create_mascot from close siblings such as animate_mascot or edit_mascot, so it stops short of a 5.

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?

It gives clear selection guidance: use prompt for a new design or image_url for an existing image, and choose engine clips or rebuild. It also routes realistic-style motion additions to create_clip. It does not give explicit when-not-to-use guidance or name the other sibling tools for editing or animating existing mascots.

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