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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds meaningful context beyond the annotations: models are canary-verified, currently promoted into the default routing pool, and served at $0 per token. This helps an agent understand what the returned set represents.

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?

A single, well-structured sentence that front-loads the core fact (free models), adds verification context, and states pricing. No filler or repetition of the annotations.

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, read-only listing tool, the description is complete. It explains what is included, why it is trustworthy, and the key property ($0 per token). No return format is specified, but the absence of an output schema is mitigated by the simple nature of the tool and its obvious list semantics.

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 takes zero parameters and the input schema is empty, so the baseline applies. The description adds no parameter details because none are needed; there is no schema gap to compensate for.

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 identifies the resource (canary-verified FREE models promoted into Flow AI's default routing pool) and the key attribute ($0 per token). It stops short of an explicit imperative verb like 'List', but the intended action is obvious from the name and phrasing.

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 rather than stated: an agent can infer this tool is for discovering currently available free models. There is no explicit guidance about when to choose it over siblings like search_models or get_live_prices, and no exclusions or alternatives are mentioned.

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