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

Annotations already convey readOnlyHint=false, idempotentHint=false, and destructiveHint=true, so the description is not required to repeat those. It adds valuable context by noting that generation consumes 'Claude Imagine credits' and that the result returns an inline image plus a full-resolution URL. This gives the agent useful expectations about cost and response shape.

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 two sentences with no filler. The core action is front-loaded, the return behavior is stated, and the sibling alternative is placed at the end. Every sentence earns its place and the structure is easy to scan.

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 tool with 3 parameters, full schema coverage, and no output schema, the description is complete enough: it states the action, the resource consumed, the return value, and the key alternative. Nothing needed to call the tool correctly is missing. The schema covers the remaining model and aspect-ratio choices.

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%, so all three parameters are already documented with descriptions, enums, and defaults. The tool description does not need to add parameter-level detail. The model description in the schema already includes guidance about defaults and trade-offs, so the description adds no extra semantic value here.

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 action: 'Generate an AI image from a text prompt.' It also distinguishes itself from the closest sibling, edit_image, by explicitly directing changes to existing images to that tool. The purpose is unambiguous and easily selectable from the sibling list.

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 explicitly tells the agent when not to use this tool: 'To change an existing image, use edit_image.' This provides a clear alternative and a condition for choosing it. The rest of the sibling tools are also clearly differentiated by the focus on image generation from a prompt.

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