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

With no annotations, the description carries the burden of disclosing behavior. It makes clear this is a read-only enumeration operation and adds useful extra context that image generation consumes credits, which helps agents reason about downstream costs. It could be more explicit that the listing itself does not consume credits, but the verb 'List' strongly implies a safe read.

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 a single, front-loaded sentence that states the action and the key output dimensions. Every word contributes meaning, and the credit note adds useful context without bloat.

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 zero-parameter list tool with no output schema, this description is complete: it tells the agent what resource is listed and what attributes will be returned. No critical information about invocation or expected behavior 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?

The tool has zero parameters, so there is no parameter ambiguity to resolve. The baseline for zero-parameter tools is 4, and the description appropriately focuses on the output content rather than parameters.

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 names a specific verb ('List') and resource ('available image models'), and specifies the key attributes returned (modes, aspect ratios, qualities, credit labels). This clearly differentiates it from sibling tools like get_image_model (singular) and list_music_models/list_video_models (different resources).

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 clearly states what the tool is used for: listing available image models with their supported attributes. It implies this is the right tool when an agent needs to enumerate image models and their capabilities, though it does not explicitly call out alternatives or exclusion conditions.

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