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

Annotations are thin (only destructiveHint=true), so the description carries most of the burden and delivers: it discloses per-image/megapixel billing and that URLs are returned by default rather than base64 to keep responses small. It does not mention auth/permission requirements, but the cost and response-shape disclosures are genuinely useful context beyond the 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 compact sentences, each earning its place: the core action, the billing caveat, the response-format default, and the endpoint. Front-loaded and waste-free.

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 12-parameter generative tool with no output schema, the description covers the cost model, the default output shape, and the default encoding, which is what an agent most needs before invoking. Minor gaps (model selection guidance, editing-vs-generation behavior of image_url) remain but nothing critical is missing.

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 83%, so the schema already documents nearly all 12 parameters (n, model, steps, width/height, prompt, response_format, etc.). The description only echoes the response_format default, adding little param-level meaning beyond the schema; baseline 3 applies.

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 ('Generate images from a prompt') plus the underlying endpoint (POST /images/generations). No sibling tool covers image generation, so no differentiation is needed and the purpose is unambiguous.

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?

Usage is implied by the generation task, and the description notes the default response_format behavior, but it gives no explicit when-to-use guidance, no prerequisites (e.g., which models support image_url editing), and no conditions under which an agent should pick it over a chat completion.

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