Generation models and prices

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint), so the bar is lower; the description still adds non-obvious behavior: unknown model/tier ids are rejected and pricing varies substantially between tiers, which shapes how an agent should use the returned data. It does not describe ordering, pagination, or the shape of returned entries, which keeps it short of a 5.

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 sentences, front-loaded with what the tool returns followed immediately by the actionable call-order rule. Every clause earns its place; nothing is restated from the title or schema.

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?

With no output schema, the description carries the burden of describing returns and does so explicitly (tiers, aspect ratios, durations, per-image/per-second credit cost). Combined with the call-ordering instruction against generate_image/generate_video, an agent has everything needed to invoke it 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?

The tool takes zero parameters, so the baseline is 4. The description's mention of tiers, aspect ratios, durations, and credit costs refers to returned data rather than inputs, and adds no parameter meaning — correctly so, since there are none.

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 and resource ('the image and video models available') and enumerates exactly what each entry carries: tiers, aspect ratios, durations, and per-image/per-second credit cost. This cleanly separates it from sibling listers like list_slideshows and from the generation tools themselves.

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 an explicit call-order directive ('CALL THIS BEFORE generate_image or generate_video') and the concrete reason: model and tier ids are not guessable and an unknown one is rejected. It even supplies a decision rationale (tier price differences are large enough to warrant deliberate choice), leaving nothing to inference.

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