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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so 'creates no media and spends no credits' is largely redundant with the structured safety profile. The one genuinely new behavioral claim is 'Reports usage-based estimates and missing inputs explicitly', which tells the agent the response surfaces gaps — useful, but the rest adds little beyond annotations.

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?

Three short sentences, each earning its place: purpose, prerequisite/routing, and behavioral guarantees, with the read-only cost-estimate framing front-loaded. 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?

For a 15-parameter, multi-modality estimation tool with no output schema, the description is minimally adequate: it explains intent and safety but leaves the agent guessing which parameters matter for a given media type. It also does not indicate whether unsupported parameters are ignored or rejected.

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?

With 15 parameters at only 27% schema description coverage, the description should compensate but does not: it only says to 'specify all billable settings' without indicating which of duration/frameCount/resolution/aspectRatio/characterCount/etc. apply to which modality. The model-ID pointer repeats what the schema already documents for the 'model' property.

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 gives a specific verb and resource — 'Get a read-only USD quote for an image, video, or audio generation' — so the agent immediately knows this estimates cost rather than producing media. However, it never differentiates itself from cost-adjacent siblings like get_pricing_info or get_balance, 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 states the context of use ('before requesting approval') and a concrete prerequisite ('Select an exact model ID from get_model_catalog'), which is actionable routing guidance. It does not name any alternative tool or exclusion case, so it isn't a full 5.

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