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

The description adds useful behavioral context not present in annotations: cost per call (~$0.08) and return format (PNG URL(s)). Annotations already indicate a non-read-only, non-destructive operation, and the description does not contradict them, but it adds concrete operational details.

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 exceptionally concise: one sentence with three key facts (generate image, model, cost, return format). Every word earns its place, and the main action is front-loaded.

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 simple two-parameter generation tool, the description is nearly complete: it names the model, price, and return format, and an output schema is present so return values are already structured. Minor gaps include lack of rate limits or content restrictions, but these are not critical given the tool's simplicity.

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 the baseline is 3. The description does not add any parameter-specific meaning beyond what the schema already provides (e.g., 'What to draw' and aspect ratio options).

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 function: 'Generate an AI image' with a specific verb and resource. It also names the model variant and differentiates from sibling tools like ai_music and ai_video.

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 name and purpose ('generate an AI image') but there is no explicit guidance on when to use it vs alternatives, nor any exclusions or conditions. It simply states the action, cost, and return format.

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