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

Annotations already establish this as a safe, closed-world read (readOnlyHint=true, openWorldHint=false). The description adds genuine context beyond that: pricing is quoted in EUR and USD while the user is billed in account currency, and reference images carry an extra charge. It does not discuss ordering guarantees or pagination, so it stops short of a 5.

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 sentences, front-loaded with what is returned, followed by the parameter rule and the selection policy. Every sentence changes agent behavior and none is redundant.

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?

With no output schema, the description takes on the burden of describing the return payload and does so (best-for notes, per-resolution pricing in two currencies, reference-image surcharge), while also covering the sole parameter and downstream selection policy. Nothing needed to call this one-parameter read tool correctly 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 coverage is 0%, so the description must carry the single boolean parameter, and it does: 'all' is documented as the switch for models not in the curated list, with an explicit default behavior of curated-only. The only minor gap is that it never states how exhaustive the 'all' set is.

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 states a specific verb (list) and resource (curated image models) and details exactly what the listing contains: best-use notes and per-image pricing by resolution in EUR/USD plus reference-image surcharges. This clearly separates it from the action siblings (generate_image, upscale_image, etc.), which mutate or produce images rather than enumerate models.

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?

It gives explicit conditional guidance for the one parameter: 'Set all=true only if the user asks for a model not listed.' It also supplies an agent-facing decision policy ('Choose the model yourself; never ask the user to pick between variants'), which tells the agent how to act on the results rather than just what they contain.

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