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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new context beyond those hints: no authentication is required and no private audio access happens. It stops short of describing the link format or expiry, so it is useful but not exhaustive.

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 with zero waste: the purpose and its auth/scope caveats are front-loaded, and the routing sentence comes last. Every clause earns its place.

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 does state what is returned (the official public streaming destination) and covers auth and scope. The one residual gap is that no usable parameter identifies which song, so the 'companion song' must be inferred from ambient context.

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 every parameter is explicitly documented as unused ('not read by this operation; omit it'), so the schema fully carries the burden. The description adds nothing about parameters, but none is needed; baseline 3 applies for a high-coverage 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?

States a specific verb and resource ('Return the official public streaming destination for the companion song') and immediately bounds scope by clarifying it does not retrieve or play the master recording. An agent can distinguish this from get_song_dossier and search_lyrics without opening any schema.

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 get_song_dossier for broader public song metadata or search_lyrics for the official public lyric record,' naming both alternatives and the condition that selects them. It also states a when-not condition (does not retrieve/play the master recording).

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