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

With no annotations, the description carries the full burden and does so: it discloses that credits are held for every direction on acceptance and charged only for returned sheets with refunds on failure/cancel, that it is an async job returning {id, status} to poll via getApiJob, and the result shape (one sheet per direction with spritesheet_url, grid fields, fps, render_3d).

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 action and stays content-dense with almost no filler, though it is a long single paragraph that could be split for scannability. Every sentence still carries actionable information.

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, annotation-free tool with no output schema, the description covers inputs, cross-tool prerequisites, async job contract, credit/refund behavior, and return payload — everything needed to invoke and follow up correctly.

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 property descriptions are rich for the nested fields, but the description adds relationship-level meaning the schema does not: the mutual exclusivity of animation_url/preset_id/model_animation, the rig requirements, and how directions render together on a shared frame/scale/floor. It largely complements rather than repeats 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 concrete verb+resource+output: 'render a 3D model into one spritesheet per direction, in a style.' This clearly distinguishes it from createDirectionalStills (stills) and previewDirectionalSprites (preview) without needing 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?

Explicitly routes the agent to prerequisites and alternatives: use create3DModel with rig or rigModel for a rigged model, listDirectionalSpriteStyles to pick style_id, previewDirectionalSprites to check first, and the animate tools for animation_url/preset_id. It also states the 'at most one animation' exclusion.

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