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

Annotations only declare a non-readonly, non-idempotent, open-world generation call; the description adds substantive behavior beyond that: dual billing rails (site credits vs. USD wallet), a ~360-credit default cost, and a two-step quote-then-confirm flow. It does not explain async behavior or how results are retrieved (get_job), which would round this out.

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 what the tool makes, then the billing mechanics. Dense but every clause carries information; the billing sentence is compressed to the edge of readability 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 6-parameter, non-idempotent, 360-credit generation tool with no output schema, the description covers the critical decision surface: cost model, quote-then-confirm safety, and per-auth billing fields. The only gap is what happens after submission (result retrieval/polling), which an agent would need to guess.

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%, so prompt, image, image_url, currency, max_credits and max_usd are already fully documented, and the description largely restates that billing pairing. It does add the useful constraint 'never convert max_credits' and the credit-cost magnitude, but the schema does most of the work, so 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?

The first clause names a specific verb and resource — building a short audio scene of sound effects, ambience and acted voices — which implicitly separates it from siblings like create_music and create_speech. It stops short of naming those siblings explicitly, so an agent must infer the boundary from the phrasing.

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?

The description gives a concrete approval workflow: omit approval to get a quote, then confirm max_credits (OAuth) or currency/max_usd (API keys). That is genuine usage guidance, but there is no when-to-use-this-vs-create_music/create_speech guidance, so an agent choosing among audio tools gets no help.

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