Add an animation

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

Annotations already declare this as a non-read-only, non-idempotent, non-destructive mutation, so the safety profile is covered. The description adds one genuine domain behavior ('looping animations should end on the pose they start with'), but says nothing about duplicate names, whether the new animation is returned or how it is addressed later, or what happens when length conflicts with later keyframes.

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 sentences, front-loaded with the purpose and followed by the one non-obvious rule. Nothing is redundant, though the second sentence is somewhat cryptic without context about pose matching.

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 three-parameter mutation with no output schema and no nested structures, the core is present: what it creates, examples, and a looping constraint. Missing pieces are modest but real — how the created animation is referenced afterward and how it relates to add_keyframes.

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 67%: 'loop' and 'length' are documented in the schema, while 'name' is only constrained by a regex pattern. The description adds a small amount of meaning around looping behavior but never explains the name pattern, the loop/once/hold modes, or the length default, so it does not compensate for the gap.

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 uses a specific verb and resource ('Adds an animation') and gives concrete examples ('idle, walk or attack') that make the domain obvious. It does not explicitly distinguish itself from nearby siblings such as add_keyframes or add_bones, so it stops short of a 5.

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 statement about when to call this versus add_keyframes or when not to call it, and no prerequisites (e.g. whether an animation must be created before keyframes can be added). The looping-pose sentence is an authoring constraint, not usage routing.

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