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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is free. The description adds genuinely new behavioral facts: durations cap at the plan's maximum, Standard/Studio pricing is expressed as credits per second (and per second with code screens), and resolutions follow a '4K policy'. It omits the paging/cursor behavior of the voice listing, which lives only in the schema.

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?

It is a single long run-on sentence with nested parentheses and comma-lists, which is hard to parse but is admittedly dense with real content rather than filler. The front-loading is good (scope stated first, call-to-action last), but the middle collapses a dozen distinct value domains into one breath, and a short bulleted breakdown would have been far more scannable.

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?

With no output schema, the description carries the burden of explaining the return shape, and it only loosely gestures at it by naming the categories. It never says how the response is organized, that the voice_* fields yield paginated results with voice_filters.accent and voices_next_cursor, or how the caller should interpret the two very different response modes. Adequate for a lookup tool, but an agent could still be surprised by the output.

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%, so the eight voice_* parameters are fully documented in structured form and the baseline is 3. The description mentions 'languages, voices and music moods' only as output categories and never explains that supplying 'language' switches the response to a filtered, paged voice list — the single most consequential parameter behavior. It neither adds nor contradicts, so it stays at baseline.

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 framing: 'Every accepted value for create_project / request_variant', which makes clear this is a static options/enumeration lookup rather than a data fetch. The parenthetical list of categories (goals, platforms, aspect ratios, durations, paces, qualities, resolutions, languages, voices, music moods) pins down the resource. It does not directly contrast with siblings like get_estimate or get_credit_balance, which also sound option-adjacent.

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 closing line 'Use it instead of guessing ids' gives a clear trigger, and naming create_project / request_variant as the consumers tells the agent when in the workflow to call it. There is no explicit when-not-to-use or note that values depend on plan tier in ways that could make a cached answer stale, but the core routing signal is present.

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