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

Annotations already declare the mutation profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false), so the bar is lower, yet the description adds genuinely new behavior: a 2-credit charge billed only on success, and identity anchoring to each mascot's reference sheet so output stays on-model. Both are things an agent cannot learn from the structured fields and directly affect whether it retries or how it forecasts cost.

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 sentences, front-loaded with the core action, then cost, then the return contract. Every clause carries information an agent needs; nothing is padding.

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?

Covers the action, the optional variations, the pricing model, the on-model guarantee, and the handoff to check_generation. With an output schema present and 100% parameter coverage, no further explanation of return values or argument formats is required.

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% and the parameter docs are unusually thorough, including the mascot_id fallback chain and the rationale for a two-character maximum. The description only restates the prop and second-mascot options already in the schema, adding no parameter-level meaning of its own — the baseline 3 applies.

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?

Opens with a specific verb and resource — renders a mascot performing an action — plus the optional prop and second-mascot variations, which separates it from create_mascot and create_prop. It doesn't explicitly contrast itself with create_animation, the nearest ambiguous sibling, so an agent must infer the static-vs-animated boundary.

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?

Names the follow-up action precisely ('Returns a generation_id for check_generation'), which is concrete routing guidance, and states the cost up front so the agent can weigh it. There is no explicit when-not-to-use clause versus create_animation, so the puzzle of pose-vs-animation selection is left implicit.

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