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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful billing behavior (paid lookups, repeated requests may re-purchase data), but the pricing passage is self-contradictory — 'at least 10 Nexscope credits' versus '1 credit per request' — and reads as pasted supplier boilerplate, so the agent cannot derive a reliable cost. No information about the returned payload or failure modes.

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?

The first two sentences are well front-loaded and precise, but the remainder is a run-on block of scraped pricing text ('Apple Music Track API View Pricing Get Apple Music track 1 credit per request... Examples are not guaranteed prices') that repeats itself, conflicts with the earlier credit figure, and does not help an agent decide or call.

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?

For a simple two-optional-parameter read tool with no output schema, the core lookup semantics are covered and the return type ('song details') is named. However, since neither id nor url is required, the description should state that at least one must be supplied and what happens otherwise — a real gap for correct invocation.

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%, so both parameters are already documented, including the album-track/url distinction. The description adds only the extra detail that album track URLs carry an i= song id, a marginal gain over the schema. Baseline 3 applies when the schema does the heavy lifting.

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 first sentence gives a specific verb and resource: 'Retrieves public Apple Music song details by id or URL.' Combined with the name and the sibling set (album, artist, search), an agent can tell this is the single-song lookup. It does not explicitly name the sibling tools it is not, 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?

The description implies usage via 'by id or URL' and notes album-track URLs are supported, which is useful selection guidance between the two input modes. It never states when to use this instead of social_apple_music_search, social_apple_music_album, or social_apple_music_artist, and gives no prerequisites or exclusions.

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