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

Annotations already declare this a safe, idempotent, non-destructive read. The description adds genuinely new behavioral context: the returned library link is private and requires the owner's normal website login, and lyrics are only present conditionally. That auth/permission disclosure is exactly the kind of detail annotations cannot convey.

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, no redundancy, with the core purpose front-loaded and the conditional/auth caveats following in order of importance.

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 usefully previews what comes back (the song plus a private library link, lyrics conditionally). The only gap is any mention of the 'id' parameter's meaning or lookup behavior, but for a two-parameter read tool this is close to complete.

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 0%, so the description must carry parameter meaning. It explains includeLyrics ('lyrics are included only if requested') but says nothing about 'id', leaving half the parameters undocumented beyond their types. Partial compensation for the coverage gap.

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 ('Get one owned song') and clarifies the scope is a single item, which implicitly separates it from 'list_songs'. It does not explicitly name any sibling, 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?

'Lyrics are included only if requested' implies how the includeLyrics flag is used, and the login note is a prerequisite for actually consuming the returned link. However, there is no explicit when-to-use vs when-to-prefer-an-alternative guidance against siblings like list_songs or get_song_job.

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