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

With no annotations present, the description carries the full burden and does so thoroughly. It states the method and shape ('Synchronous GET with no request body'), the exact return structure (animations array with fields, deduplicated perspectives, directions), the free/credits behavior, the retargetable clip_url condition, and the API key requirement with user scope. This far exceeds minimum behavioral disclosure.

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 description is lengthy but front-loaded with the core purpose, then the return schema, then usage directions, then auth requirements. Every sentence earns its place given the lack of an output schema and annotations. The explicit list of eight compass directions and the long field enumeration make it dense, but not wasteful.

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 zero-parameter, read-only discovery endpoint with no output schema, annotations, or nested objects, the description is unusually complete. It covers what the tool returns field-by-field, how to use those results, which sibling tools consume them, the synchronous GET nature, free credit behavior, and auth scope. No meaningful information an agent needs to invoke it correctly 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?

There are zero parameters, so parameter semantics are inherently simple. The 100% schema coverage of an empty properties object leaves nothing ambiguous. The description adds useful context about what values the tool returns for downstream consumers, which is the closest analog to parameter-related guidance in this case.

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: 'List the available animation presets along with their perspectives and the eight supported compass directions.' It clearly distinguishes itself from siblings by naming transferMotion, animateSprite, and animate3DModelPreset as related tools that consume this tool's output, and by emphasizing it is a discovery endpoint rather than an animation-applying tool.

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?

It explicitly tells an agent when to use this tool: to obtain preset_id, perspective, and direction values for transferMotion, and to find preset names for animation. It also names related sibling tools that the presets can be paired with. There is no explicit 'do not use when...' exclusion, but the discovery-vs-application contrast is clear.

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