list_users_online

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

Annotations already declare this as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds no behavioral context beyond the HTTP endpoint, such as what 'online' means, session semantics, pagination, or authorization requirements.

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 extremely concise, with the core purpose front-loaded in the first sentence. The endpoint line is arguably redundant but harmless. No filler or unnecessary details are present.

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?

Given there are no parameters, an output schema exists, and annotations cover the operation's safety profile, this is nearly complete for a simple list operation. The only notable gap is not explaining what qualifies a user as 'online' or whether special context is needed.

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 schema is trivially complete, so the description has no parameter semantics to explain. The baseline of 4 applies for parameterless tools.

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 clear verb and resource: 'Get users online.' It distinguishes from siblings like list_users by the 'online' qualifier. However, it mostly restates the tool name and does not add clarifying detail about what 'online' means in this system.

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?

Usage context is only implied by the phrase 'users online' — an agent can infer it is for retrieving currently online users. There is no explicit guidance about when to prefer this over list_users or any other alternative, and no exclusion criteria.

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