katto_translate_captions

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

Annotations already declare non-read-only and non-idempotent, and the description reinforces this while adding material context the annotations lack: the original clip is preserved, only captions change, word timings are kept, no video quota is used, and auth/paywall failure emits upgrade_required with a pricing link. It even documents the async follow-up (rerender_id → poll katto_get_rerender).

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?

Dense but tightly front-loaded: the core action and constraint come first, then scope limits, then auth/paywall, then the async return contract. Every sentence carries distinct, non-redundant information.

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 mutation/render tool with no output schema, the description closes the remaining gaps by explaining the return value (rerender_id) and the polling path to the new clip_url, plus preservation semantics and cost/auth implications.

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 coverage is 100% and the enum already lists the 19 languages, so the schema carries the parameter detail. The description adds only the language count and the notion that timings are preserved; it adds no per-parameter syntax or format beyond the schema. Baseline 3 is appropriate.

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+scope ('Translate one finished clip's burned-in captions') and explicitly distinguishes itself from the sibling katto_dub_clip ('for a translated VOICE use...'). An agent can route between the two without opening either 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?

Names the alternative tool and the condition that selects it (voice vs captions), states the Creator-subscription prerequisite and the resulting error code, and clarifies it does not consume video quota. When/when-not is fully covered.

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