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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description earns credit for adding 'online null when hidden' and 'Counts as browsing' — a non-obvious side effect that the target's browsing activity is recorded. However, that phrase is cryptic and neither its consequences nor any rate/permission constraints are spelled out.

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?

Very short and front-loaded — the core purpose and the null-when-hidden edge case come first. The trailing fragment 'Counts as browsing' is terse to the point of ambiguity, but nothing is redundant.

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 should carry return-value semantics; it covers online and last-seen at a high level but gives no format or resolution for the timestamp and never explains account_id, leaving gaps for a simple two-param tool.

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 50%: user_id is well documented in the schema, while account_id has only a uuid format. The description adds nothing about either parameter, so it neither compensates for the gap nor overrides the schema baseline.

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 the resource (a person's presence) and what it returns: current online state plus last-seen time. It is clearly distinguishable from the sibling list_user_* / get_profile tools, though it never explicitly contrasts with them.

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?

There is no statement of when to call this versus alternatives and no prerequisites or exclusions. The only guidance-adjacent content is the parenthetical about hidden presence, which explains an output case rather than when to use the tool.

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