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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely new information: the fallback to the newest rigged version when the model is unrigged, and the 'Free.' cost note, which no annotation conveys. It stops short of describing what an empty or unrigged-forever model returns.

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 compact sentence that front-loads the return payload, plus a one-word cost signal. The elliptical grammar of the second clause ('for a model that is not rigged, of its newest rigged version') is slightly harder to parse than it needs to be, but no sentence is wasted.

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?

No output schema exists, and the description does explain the return shape (names and durations), so an agent knows what to expect. With one fully documented parameter and annotations covering the safety profile, little 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 100% and the single model_id parameter is already documented in the schema with its source tools. The description adds nothing about the parameter itself, only about the model's rigging state, so baseline 3 applies.

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 the concrete resource (animation clips) and what is returned (names and seconds), which is more specific than the title alone. It also discloses the resolution rule for unrigged models, which distinguishes it behaviorally from a plain get_model, though it never names a sibling tool explicitly.

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: fetch animations for a given model. The conditional clause about non-rigged models falling back to the newest rigged version is helpful context, but there is no explicit when-to-use/when-not guidance and no pointer to an alternative for obtaining animation data.

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