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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description earns credit by disclosing the shape of the returned payload — performer, release, year, length, and related tracks — which annotations and the input schema say nothing about. It omits failure behavior for an unknown track_id, which keeps it from 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?

One compact sentence with the primary subject ('One song') front-loaded and the returned fields enumerated without filler. Nothing could be removed without losing 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 must carry the return-value burden, and it does list the key fields a caller would get back. Missing only edge-case context such as what happens when the track_id does not resolve, which is a minor gap for a read-only single-record lookup.

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% and the single parameter already carries its catalog-id description and a 22-character pattern, so the schema does the heavy lifting. The description adds no meaning about the id — no note that it must be an exact catalog id or where to obtain one. A 3 baseline is appropriate.

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?

The description names the resource ('One song') and enumerates exactly what it returns — performer, release, year, length, and other tracks by the same artist — so an agent knows this is a single-track lookup with bundled context. It stops short of an explicit retrieval verb or of naming how it differs from get_album/get_artist, but the resource and payload are unambiguous.

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?

There is no when-to-use guidance and no exclusions. The phrase 'more songs by the same artist' overlaps conceptually with similar_tracks, yet the description never says which tool an agent should prefer for that need, nor when to reach for search_catalog instead of a direct id lookup.

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