estimate_cost

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

Annotations already indicate readOnlyHint and idempotentHint. The description adds behavioral details: it runs the same provider auto-selection as generate_image, uses a local pricing table, and notes the estimate is a ballpark. No contradictions.

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 well-structured: starts with purpose, then explanation, caveats, and finally Args/Returns. It is slightly verbose but front-loaded with key information. A bit more conciseness could improve it.

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 simplicity of the tool (cost estimation with no side effects), the description covers all essential aspects: what it does, how it works, caveats, and return format (via output schema). With annotations and output schema present, no gaps remain.

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 description's Args section briefly lists parameters but adds little new meaning beyond the schema's own descriptions. The schema already provides detailed descriptions for each parameter. Schema coverage is 0% by context definition, but the schema itself is informative, so the description does not compensate for missing schema details.

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 clearly states the tool's purpose: estimating the cost of generating an image without actually generating it. It uses specific verb 'estimate' and resource 'cost', and distinguishes it from siblings like generate_image by explicitly noting it does not generate.

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 explains when to use: before generating, for comparing providers/qualities. It implies not to use for actual generation, but does not explicitly state when not to use or list alternatives beyond the tool itself. However, the sibling list provides context.

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