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

With no annotations, the description fully carries the burden. It transparently discloses async behavior ('Async — returns requestId, poll with check_job_status'), cost ('1600 sats per model'), and the authentication model ('no API key or signup needed'). It also names the underlying model (Tencent Hunyuan3D), adding significant behavioral context beyond the schema.

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 is composed of six short, information-dense sentences: purpose, model/provider, async behavior, cost, payment method, and prerequisite. No fluff or repetition; every sentence earns its place.

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?

Given the tool's complexity (async, paid, multi-input) and lack of output schema, the description covers all essential aspects: input formats, output type, provider, cost, payment flow, and follow-up polling. It is sufficiently complete for an AI agent to invoke the tool 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 coverage is 100%, so the baseline is 3. The description adds payment context ('Requires create_payment with toolName='generate_3d_model'') relevant to the paymentId parameter, and reinforces the exclusive-or relationship between prompt and imageBase64, though this is already in the schema. This modest addition justifies a 4.

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 opens with 'Generate a textured 3D GLB model from EITHER a photo OR a text prompt,' clearly stating the tool's function and output format. This distinguishes it from sibling 2D generation tools like generate_image and generate_video.

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 description provides explicit usage constraints ('provide exactly one, not both') and outlines the async workflow ('poll with check_job_status') and payment prerequisite ('Requires create_payment with toolName='generate_3d_model''). While it doesn't explicitly compare to alternative 3D tools, no other 3D generation tool exists in the sibling list, so the guidance is clear and actionable.

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