List currently online clients

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds that it returns emails and filters by online status, which is useful but not extensive. No mention of edge cases like empty lists, ordering, or pagination, but given annotations the description carries a reasonable load.

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 description is a single, clear sentence that front-loads the action ('List') and immediately specifies the scope ('emails of clients that are currently connected/online'). No wasted words or redundant phrasing.

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 simple, parameter-less read-only list tool, the description adequately specifies the return type (emails) and the filter (online status). While it lacks details like ordering or pagination, the simplicity of the tool reduces the need for more, and the annotations already cover safety. The presence of sibling 'list_clients' is implicitly understood.

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, and the description correctly avoids mentioning any. Per the rubric, a parameter count of 0 sets a baseline of 4, and the description adds nothing more because there is nothing to add.

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 clearly states the verb 'List' and the resource 'clients' with the qualifier 'currently connected/online.' This unambiguously distinguishes it from the sibling tool 'list_clients' (which presumably lists all clients) without needing to name the sibling explicitly.

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 implication that this tool is for online clients is clear, but there is no explicit guidance on when to choose this over 'list_clients' or any alternatives. It relies on the user/agent to infer usage context from the description alone.

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