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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds genuinely non-structured context: keyframes are stamped in SOURCE frames (with the exact conversion formula) so they survive moves and trims, and 'clear' with property omitted wipes ALL animation. That destruction scope is important and would be invisible otherwise; unit/value ranges per property remain unspecified.

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-loaded with the core purpose, then property list, then coordinate semantics, then action modes — a sensible order with little filler. The inline property enumeration is long but each entry is load-bearing as the allowed-value set.

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 10-parameter mutation tool with no output schema, the description covers the hard parts: coordinate space, action semantics, easing direction, and the effect-vs-property path. What is missing is value domain information (units/ranges for scaleX, rotationDeg, opacity, etc.) and any hint about what a successful call returns or confirms.

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 goes beyond the schema by defining the source-frame coordinate system (`timelineFrame - startFrame + trimStartFrame`) and clarifying that `easing` describes how a value LEAVES a keyframe. These are the two most error-prone parameters and the description meaningfully disambiguates them.

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 opening verb phrase 'Animates one clip property' is specific, and the enumerated property list makes the scope unambiguous. It never names `set_clip_properties` or `manage_effects` as the non-animated/effect counterparts, so sibling differentiation is left implicit rather than stated.

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?

The three action modes (set/remove/clear) and what each does are explained, which gives real usage direction. But there is no explicit guidance on when to animate here versus using `set_clip_properties` for a static value, or when to route to `manage_effects` for effect params — the agent must infer that.

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