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

Beyond the annotations' read-only and non-destructive hints, the description discloses the activity window (last 15 minutes) and the privacy-relevant detail that only members who show their online status are named. This is useful behavioral context that structured annotations do not provide.

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 definition is three short sentences, front-loads the primary purpose, and adds a Returns section without redundant elaboration. Every sentence contributes new information.

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 zero-parameter, read-only tool with an output schema and clear annotations, the description fully covers what the tool returns and the meaning of the data. There is no missing operational detail an agent would need to invoke it correctly.

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?

The tool has zero parameters, so there is no parameter documentation burden; the baseline of 4 applies. The description is entirely sufficient for calling the tool without further parameter guidance.

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 states a specific resource (current online presence on WindowsForum) and the exact metrics returned (member/guest/robot counts plus visible member names). It clearly differentiates this from siblings like get_latest_registered_users and get_forum_statistics by emphasizing 'right now' and the 15-minute activity window.

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?

The opening 'See who is on WindowsForum right now' gives a clear use case: checking current online activity. The 15-minute active window sets expectations, and while it does not explicitly name alternative tools, no prerequisites or conflicting use cases are left ambiguous.

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