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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely non-obvious behavior: viewCount is null unless the track is among the artist's top tracks, the explicit label lives inside `raw`, and each call costs 1 credit. That null-vs-populated nuance is exactly the kind of conditional data behavior an agent needs.

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?

Four short sentences, front-loaded with the core purpose followed by return fields then edge cases then cost. Every sentence carries information. Minor weakness: the credit-cost note sits last when it is the kind of gating detail that could be front-loaded.

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 carries the return-shape burden and does so well by enumerating fields plus the conditional viewCount and where the explicit flag lives. What's missing is error/empty behavior (e.g. invalid id, region-restricted track) and any mention of the cache_max_age parameter.

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 only 50%: `id` is documented in the schema with accepted formats (id, spotify:track: URI, URL), but `cache_max_age` has no description anywhere. The description compensates for neither gap and devotes no text to parameter meaning, so the undocumented parameter stays opaque.

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 specific resource (a public Spotify track) and enumerates the exact fields returned: title, artists, artwork, duration, release date, preview clip URL. That is far beyond restating the name. It does not explicitly contrast itself with nearby siblings such as spotify_search or spotify_album, so it stops short of a 5.

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 statement of when to use this tool versus spotify_search (to find an id) or spotify_album / spotify_artist. The only usage-adjacent detail is the cost line ('Costs 1 credit'), which helps budgeting but not selection. The agent must infer that it needs a known track id already.

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