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

Annotations already declare destructiveHint=true, but the description goes well beyond that: it explains exactly what is destroyed (all browser logins), and critically that there is no 'current session' to preserve when called via the assistant because the assistant operates with a key, which is why close_all demands confirmation. That is precisely the kind of non-obvious behavioral context an agent cannot derive from the annotations.

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 opening sentence front-loads the resource and its two operations, and the snapshot of returned fields comes next. The close_all warning is verbose and the cabinet-vs-assistant comparison is somewhat convoluted, but no sentence is pure filler given the destructive stakes.

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 three-parameter mutation tool with no output schema, the description covers the destructive action thoroughly and the 100%-covered schema handles inputs. It does not describe the shape of the list result (fields beyond device/browser/city), but with no output schema that omission is minor.

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%, so both session_id and confirm_close_all are already documented in the schema, including that confirm_close_all implies the user is kicked out of the cabinet they are working in. The description reinforces the semantics of close_all but adds little that is not already in the schema text, so the baseline 3 is appropriate.

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 description names a specific resource (active account sessions/logins) and the operations (listing entries and closing redundant ones), plus what data is exposed (device, browser, city, last login). It is clearly distinguishable from siblings like get_user_me or update_user_profile, which touch the account but not its sessions. It stops short of a crisp one-line verb+resource statement because the purpose is delivered as prose rather than a header.

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?

It gives explicit guidance for the risky path: close_all closes every browser session including the one the person is currently using in the cabinet, and therefore requires confirmation. That is a clear when-to-be-careful rule. However, it never frames the ordinary choice between list, close, and close_all, so the routing among the three actions is left to the schema enum rather than stated in prose.

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