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

Adds real context beyond the annotations: a concrete cost signal ('$0.15/track at provider cost') and the shape of the result ('Returns an audio asset id'). readOnlyHint=false only tells the agent this is not a pure read; the description supplies the paid-generation and hand-off semantics that matter for an expensive, side-effecting call.

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?

Two sentences with the cost banner front-loaded in brackets, then purpose, then return value and next step. No filler; every clause conveys distinct actionable 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?

With no output schema, the description correctly discloses the return value (audio asset id) and how to consume it. Cost is covered. It stops short of noting whether generation is synchronous/long-running or what happens on failure, which is the main remaining gap for a paid generation tool.

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% with per-parameter descriptions for mood, project_id, and duration_seconds, so the schema carries the parameter burden. The description reinforces 'mood/style description' but adds no constraints (duration limits, free-text vs. enum behavior) beyond what the schema states. 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?

States a specific verb and resource ('Generate a background music track') plus the input modality ('from a mood/style description'). Distinguishes itself from the nearby studio.generate_scene and studio.generate_voiceover by naming the output as a music/audio track, and even names the downstream consumer add_audio_to_timeline.

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?

Gives clear next-step context — 'place it with add_audio_to_timeline' — which is the primary usage path for this tool's output. It does not explicitly exclude alternatives (e.g., importing an existing track via studio.import_asset_from_url or adding an uploaded asset), so the when-not guidance is absent.

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