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

Annotations already cover read-only, idempotent, non-destructive, and open-world, so the description adds the remaining operational facts: an auth precondition ('Auth: linked') and an explicit instruction not to prompt the user for the id. It stops short of describing the failure mode when no account is linked, which is the one behavioral gap.

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 labeled lines (purpose, Use, Inputs, Returns, Auth) with no filler, and the identity statement is front-loaded. Every line carries information an agent would otherwise have to infer.

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 and no parameters, the description supplies exactly what's missing: the returned fields (data.id, data.name, data.account_mode, data.linked_since) and the auth requirement. An agent has everything needed to decide to call it and to parse the result.

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?

Zero parameters, so the baseline is 4; the description reinforces this with an explicit 'Inputs: none,' removing any doubt that no arguments are accepted. Nothing further could be added.

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?

Clearly identifies the resource: the linked account's stable opaque profile id plus display name, with a concrete directive ('never ask the user for it'). It doesn't need sibling differentiation because all listed siblings target unrelated resources (artists, tracks, labels, festivals), so there is no ambiguity to resolve.

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?

'Use: the host needs a stable user handle; after sign-in to confirm the link' names two concrete triggering contexts. No when-not conditions or alternatives are given, but none are needed for a zero-parameter identity lookup with no real sibling overlap.

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