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

Far beyond the readOnlyHint=false/openWorldHint=true annotations, the description discloses cost per action (300 Sinapses for lyrics, 3000 for render, 0 for create and publish), a rate limit (3/min on render), async fire-and-forget semantics, idempotency of publish, curation restrictions, and the owner-scoping guarantee ('só mexe nas suas tracks'). These are exactly the operational facts an agent needs before triggering a paid mutation.

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?

One dense paragraph, but it is front-loaded with the identity and each sub-action gets a compact parenthesized definition; nothing is filler. Some pricing detail is repeated between the prose and the model parameter description, but within the description itself every clause carries operational 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 15-parameter, seven-action tool with no output schema, the description is remarkably complete: it covers the end-to-end flow, the async polling states, and roughly what each action returns (trackId, id/título/status/áudio). It stops short of describing failure/retry behavior on render or the exact shape of a publish response, which an agent would otherwise have to discover empirically.

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 already 93%, so the baseline is 3; the description earns above that by explaining cross-parameter interactions the schema only hints at — the model/durationSeconds coupling, the fixed price vs. per-duration ElevenLabs pricing, and the note that seed and negativePrompt are ignored on non-Lyria engines. The explicit pointer to the 'musica' skill for the price table is a useful addition, though a few parameters (title, context, direction) are left to the schema.

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 opening line states a specific verb and resource ('loop completo de música via voz Sapiens') and the description enumerates all seven sub-actions with one-line definitions, so an agent knows exactly what the tool covers. It does not, however, name any sibling tool (e.g. sapiens_stock_audio, sapiens_trilhas) to disambiguate which one to reach for, so it stops just short of a 5.

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?

It gives explicit when-to-use guidance per sub-action, states the preconditions (any logged-in user for most actions; admin/owner only for publish; list_public needs no login and no cost) and spells out the intended flow: create → lyrics(trackId) → render → get (poll rendering → ready/failed) → publish. The lyrics branch even explains the two modes (with vs. without trackId) and what each produces.

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