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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds genuine value by disclosing the composition of the result set (library + personal uploads + prior generations) and that tempo and length are included. It says nothing about ordering, result limits, or what happens when mood matches nothing.

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, no filler: the first defines the resource and its contents, the second draws the boundary against the generation sibling. The exclusion is placed last where it belongs, and the parenthetical enumerations stay tight.

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 rich annotations, full schema coverage and an output schema that documents the returned shape, the description only needs to establish scope and routing, which it does. The one real gap is disambiguation from the other list-style music siblings, which an agent browsing this crowded toolset would still have to resolve by trial.

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%, with both mood and listingId documented in the schema including an example vocabulary for mood, so the baseline is 3. The description adds no parameter-level meaning beyond that, not even noting that mood is an optional free-text filter.

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 ('lists existing tracks this listing can use') and enumerates the pool it draws from (royalty-free library, own uploads, earlier generated tracks), plus what each entry carries (BPM, length). It is clear on its own, but among the many music siblings it only explicitly distinguishes itself from request_music_generation, leaving list_songs, list_generated_music and propose_music undifferentiated.

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 an explicit when-not with the named alternative: 'It lists existing tracks only; a new original track is made with request_music_generation.' That is a real routing rule. It stops short of explaining when to filter with mood or when another listing tool (list_songs, list_generated_music) is the better choice.

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