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

Annotations already declare the operation non-read-only, non-destructive, and closed-world, so the safety profile is covered. The description adds real behavior beyond that: imported colours become generated props color1… by usage frequency, words become text1…, playback is frame-exact in preview and export, and with brandColors the brand kit's colours replace the file's own, joining the project brand's pack. It does not say what happens on failure or with an unreachable URL, so a 4 rather than 5.

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?

The core action and the json-or-url rule are front-loaded, then details follow in a logical order: derived props, playback fidelity, brand behavior. Sentences are dense with information and free of filler, though the brand-kit sentence is somewhat terse and could read ambiguously.

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 7-parameter import tool with no output schema, the description covers the essential mental model: input modes, derived props, placement, and brand interaction. Gaps remain around duration semantics and error/precondition behavior, but an agent could call this correctly from what is given.

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 only 29%, so the description has to carry the load. It explains json vs url formats, the prop-generation effect of brandColors, and start's timeline meaning, but leaves duration, projectId, and name's role unaddressed despite those being among the 7 parameters. Useful compensation, but incomplete for a low-coverage schema.

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 opens with a specific verb and resource: add a Lottie animation (bodymovin JSON) to the graphics library, with optional timeline placement. That is far more precise than the title alone and separates it from add_html_overlay or set_animation by naming the input format. It never explicitly contrasts itself with those siblings, which keeps it from 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?

"Pass json (the file's text) or url (a public https URL)" gives a clear rule for choosing between the two input modes, and "optionally place it on the timeline" clarifies that start is opt-in. However, there is no guidance on when to import a Lottie versus adding an HTML overlay, an animation, or existing library media, and no stated precondition for the neither-json-nor-url case.

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