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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so safety is covered; the description adds value by disclosing the sort order, the presence of a permanent mp3 link, the deliberate absence of playUrl, and the pagination mechanism ('after (the answer's next)'). It does not cover rate limits or empty-result behavior, which keeps it below a 5.

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 dense sentences: contents and ordering first, then return fields, then pagination, then the alternative. Every clause carries information, and the endpoint (GET /music) is tucked in last without bloat.

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 compensates by enumerating returned fields and explaining the cursor, which is what an agent needs to page correctly. Minor gaps remain: no statement about account scoping behavior when email is omitted, and no mention of the result count or empty-library behavior.

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, including the conditional requirement for email, so the schema carries the load and baseline is 3. The description only clarifies the 'after' cursor semantics ('the answer's next') and adds nothing about limit or email beyond 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?

Names a specific verb and resource (songs in an account's ACE Music Library) plus the exact contents (generated songs and uploaded audio) and ordering (newest first). It even enumerates the returned fields, so an agent knows precisely what this tool produces versus siblings like acemusic_get_song or acemusic_list_jobs.

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 routes the agent: 'Use acemusic_get_song for one song's full detail and its playUrl,' and the parenthetical '(no playUrl here)' reinforces the boundary between list and detail. It gives no when-not guidance (e.g., listing jobs or accounts instead), but the primary alternative and its selection condition are stated.

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