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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real value by disclosing ordering (newest first) and the per-device fields returned (platform, trusted for approvals), but says nothing about result limits or pagination, which matters for a list whose ordering is explicitly stated.

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?

A single dense fragment with zero filler: scope, ordering, and returned fields are all front-loaded. Nothing repeats the title or the schema verbatim enough to waste space.

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?

No output schema exists, so the description usefully names the salient returned fields and their order. For a low-complexity single-parameter read this is close to sufficient; only volume/pagination behavior is left unstated.

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 100% for the single required user_id ('Your own id for the user'), so the schema carries parameter documentation. The description reinforces the one-user-at-a-time scope but adds no format, type, or sourcing detail beyond the 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?

Identifies a specific resource and scope: the devices registered for a single user id, returned newest first, including platform and approval-trust status. It implicitly distinguishes itself from register_device/remove_device by being a read of the existing set, though it never explicitly contrasts with list_passkeys, the closest sibling.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is named. An agent must infer that this is the read-only enumeration path versus list_passkeys (credentials) or register_device/remove_device, purely from the name and from sibling context.

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