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

Annotations already signal a safe read (readOnlyHint, non-destructive, closed-world), and the description adds substantial behavioral context beyond them: it discloses the keyword-matching limitation (a 'not mentioned' principle may still exist; a 'mentioned' one may be poorly executed). It also describes the response shape (each principle with a question and an interface translation) and the 400 ms flagging behavior.

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?

Front-loads the core action and principle list, then adds the caveat and duration rule. The parenthetical enumeration of twelve principles is long but functionally necessary; wording is otherwise tight with no filler.

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, yet the description explains what comes back (per-principle question and interface translation, plus a UI duration flag), and it flags its own reliability limits. An agent has everything needed to call it and interpret results correctly.

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%, so the baseline is 3, but the description adds real meaning: it specifies what `description` should contain (what moves, how, how long, why) and frames `purpose` as the audience context. The enum values themselves are already in the schema, so it does not repeat them needlessly.

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?

States a specific verb (review) and resource (a described animation) and enumerates all twelve principles, so the agent knows exactly what will be assessed. The keyword-based nature and the 400 ms UI flag pinpoint it as a conceptual-principles review rather than a CSS/Lottie lint (check_motion, audit_motion_css), which is the key sibling distinction.

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?

Gives clear preconditions: pass `description` (what moves, how, how long, why) and optionally `purpose` (ui, marketing, illustration), and notes the 400 ms UI duration rule implies a UI-motion use case. It stops short of naming an alternative sibling or stating when NOT to use it.

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