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

Annotations already disclose the mutation profile (readOnly=false, destructive=false, idempotent=false), so the bar is low. The description adds genuinely new behavioral context — 'Costs 1 credit' — which no structured field carries. It stops short of saying what artifact/ID is returned or whether repeats create duplicates.

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?

Three short sentences, each carrying distinct load: what it produces, what it costs, and when it is warranted. Nothing is repeated and the routing condition is front-loaded enough to guide selection.

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 two-parameter generation tool with no output schema, the description covers purpose, cost, and the gating condition, which is enough to invoke it correctly. It could say what the call returns (a still/asset id) so the agent knows how to chain into animate_mascot.

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 100%, including a concrete example for 'pose' and the provenance of project_id, so the schema does the heavy lifting. The description adds no syntax, format, or constraint detail beyond it, which is the expected baseline here.

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+resource ('Draws the approved mascot in a new pose or expression') and immediately frames the output ('as another still to animate from'), which separates it from animate_mascot and create_mascot without needing the schema.

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 a clear when-to-use condition: 'Only needed when an animation should start from a different pose than the approved one.' It implies the when-not case (don't call if the approved pose is fine) but never names animate_mascot or approve_mascot as the alternative path.

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