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

Annotations only declare openWorldHint=true, leaving the description to carry most of the behavioral burden. It usefully discloses the asynchronous contract (returns a request ID, results retrieved via fetch-audio), which an agent could not infer from the schema. It does not mention auth, cost, or duration limits, so it stops short of full transparency.

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 short sentences with no filler, and the core action and its constraint are front-loaded before the retrieval note. Every sentence 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?

With no output schema, the description correctly compensates by explaining that the return is a request ID consumed by fetch-audio. Combined with 100% schema coverage this is nearly complete; only error/limit behavior is missing, which is minor for a generation task.

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 all ten parameters are already documented in the schema, including the side enum meanings. The description adds no syntax, format, or default information beyond that, so the baseline of 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 ('Extend existing music tracks') plus the scope constraint of extending from either the beginning or end. It is reasonably distinguishable from siblings like song-inpaint or music-generation, though it never explicitly contrasts itself with them.

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?

Provides a clear input precondition ('takes an existing audio file') and an explicit follow-up route ('returns a request ID that can be used with fetch-audio'), which is genuine workflow guidance. However, it gives no guidance on when to choose this over song-inpaint or music-generation, and no prerequisites for model_id.

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