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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered structurally. The description adds real value beyond that by disclosing the return payload — accepted input types and the fact that a coin balance comes back alongside the models. Pagination and result-size behavior are still unstated.

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?

Two dense sentences, front-loaded with the verb and scope; the enumerations are compressed into parentheticals and the workflow hint is a single final clause. No filler.

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?

No output schema exists, so the description carries the burden of describing the return value — and it does, listing id, name, maker, accepted aspects/resolutions/durations/voices and default coin cost plus balance. Combined with annotations that cover safety, an agent has everything needed to call it.

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 description coverage is 100% and the single enum parameter is fully documented, so the schema does the work. The description restates the same four enum values under the phrase 'one kind of creation' but adds no format or semantics beyond them. Baseline 3 applies when the schema carries the parameter meaning.

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?

Specific verb (List) plus resource (models) with an explicit scope: 'one kind of creation — image, video, speech or music.' It goes further by enumerating the return shape (id, name, maker, accepted inputs, default coin cost). It does not differentiate itself from the sibling app_models, 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?

The closing sentence 'Pass a model's id to estimate_generation and generate' states the downstream workflow, telling the agent exactly where this tool fits in the chain. There is no explicit when-not guidance or disambiguation from app_models, which keeps it out of 5 territory.

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