Estimate cost

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

Annotations already establish readOnly/idempotent/no open-world, so the safety profile is covered. The description adds real behavioral context beyond that: the call compares models only when requested and additionally surfaces remaining budget and whether approval is needed, which is not derivable from the annotation block.

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?

A single front-loaded sentence leading with the core purpose, then two appended clauses for the optional compare behavior and extra outputs. Every clause carries information, though the semicolon-chained tail is slightly dense.

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 a 100% covered schema, an output schema that documents return values, and annotations covering the safety profile, the description supplies the missing intent layer (multi-media, pre-flight, optional comparison). It is adequate for correct invocation, though it says nothing about output units or error conditions, which is acceptable given the output schema.

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 every parameter (count, model, compare, imageSize, resolution, durationSeconds, etc.) is documented in the schema itself. The description's remark about 'optionally comparing all models' duplicates the existing compare parameter description, so it adds little beyond the structured fields — baseline 3.

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 (estimate) and resource (cost of image/video/speech/music requests) and frames it as a pre-flight step ('before running it'), which implicitly separates it from the generate_*/edit_* siblings. It also names the secondary outputs (remaining budget, approval need), so an agent knows exactly what this tool returns.

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?

'before running it' gives a clear usage context: call this prior to a generation request to preview spend. It does not name explicit alternatives or when-not-to-use conditions (e.g. relation to get_usage or get_config), so it stops short of full routing guidance.

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