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

With no annotations, the description carries the full burden and does so: it discloses async behavior, expected latency, brief inline waiting, credit cost scaling by requested length, the pricing model (3 cr per started 30 s), and the polling fallback. That is exactly the behavioral context an agent needs before a paid, slow operation.

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 front-loaded: purpose, modes, cost, and polling each appear in a short clause with no filler. The parenthetical model/pricing clause is slightly compressed but still earns its place.

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 an async, credit-consuming generation tool with no output schema, the description supplies everything an agent needs: latency expectations, cost model, both input modes, and the status-polling continuation path.

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 baseline is 3, but the description adds real meaning beyond the schema: it distinguishes prompt-only from style+lyrics composition, explains section-tag line placement, and ties `seconds` to billing. Only partially overlapping with schema text, so it earns above 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?

States a specific verb and resource ('Make a song with vocals and instruments') and immediately disambiguates the scope with 'async' and 'a few minutes.' An agent can distinguish it from generate_image/generate_video/generate_speech without inspecting the 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?

Explicitly lays out the two invocation modes (single `prompt` versus your own `style` + `lyrics`) and the follow-up path ('poll get_music_status with the returned id'). It stops short of stating when to prefer a sibling like generate_speech, but within-tool routing guidance is clear.

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