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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds one genuinely new behavioral fact, 'Free to call', which is not in the annotations and is useful for cost-aware planning. It says nothing about result size, ordering, or how to handle large catalogs.

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?

Two short, front-loaded sentences with no filler; the return payload is described first and the cost note last. The telegraphic, verb-less phrasing ('Free to call.') is terse to the point of being slightly clipped but costs no clarity.

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 read-only catalog tool with no output schema and one optional param, the description covers the returned fields adequately. The main gap is that it neither explains the kind filter nor states what happens when kind is omitted.

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 0%, so the description must carry the parameter meaning, and it does not: the optional 'kind' enum filter is never mentioned. Worse, the phrasing 'Image and video models' reads as if both kinds are always returned, which obscures that a filter exists at all.

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?

Names the resource (image and video models on KeelRouter) and the payload each entry carries (USD prices per tier, accepted request params), which is more specific than the title alone. It never uses an explicit verb like 'list' or 'returns', and it does not contrast itself with siblings such as generate_image or generate_video, so differentiation is left to the reader.

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?

There is no when-to-use or when-not-to-use statement. The phrase 'the request params each accepts' hints that this is a discovery step before generation, but the agent has to infer that; no alternative tool or condition is named.

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