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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds valuable context beyond annotations: the paid cost ($0.75 USDC via x402), the fact that it only works with built-in clips, and the note that it reports coverage and deterministic hashes. This enriches the agent's understanding of the tool's behavior without contradicting the hints.

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 two sentences: the first states the purpose and outcome, the second discloses the cost and payment model. Both sentences earn their place, with no redundancy or filler. It is concise, front-loaded with the primary action, and structured for quick comprehension.

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?

Given the tool's moderate complexity (3 params, 2 required), the description covers the core functionality, cost, and a key constraint (built-in clips). It also indicates the output type (coverage + hashes) even though no output schema exists. Missing are explicit details on error behavior or output structure, but the description is adequate for an agent to select and invoke the tool 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?

The input schema provides 100% description coverage for all parameters (platform, clip_name, drop_unmapped), so the baseline for this dimension is 3. The description adds no extra parameter-level detail beyond what the schema already conveys, though it does mention 'built-in' which aligns with clip_name's schema description.

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 ('retarget') and resource ('built-in animation clip') and clearly states the outcome ('report coverage + deterministic hashes'). It distinguishes from sibling tools like axis_compare or generate_avatar_from_image by focusing exclusively on animation retargeting across platform mappings.

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?

Usage context is implied: the tool is for retargeting built-in animation clips to a specific platform mapping. However, it does not explicitly contrast with alternatives or state when not to use it, so it lacks the explicit when/when-not guidance that would merit a 4 or 5.

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