get_online_users

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

With no annotations, the description carries the full burden. It adds useful behavioral context by revealing that each user has a 'username' field and how to format it for mentions. It also uses 'recently active' rather than 'online', clarifying the inclusion criterion. Minor gaps remain, such as the definition of 'recently active' and any pagination limits, but the core behavior is well communicated.

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 two sentences with no fluff. It front-loads the purpose in the first sentence and adds a concrete example in the second, earning its place.

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 one-parameter tool with no output schema, the description provides purpose, a key output field, and usage guidance. It could mention the optional nature of 'room' or the default, but that's already in the schema. Overall, it is sufficiently complete for an agent 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 input schema has 100% coverage for the single 'room' parameter with its own description and default value. The tool description does not add any parameter-level detail, so the schema does the heavy lifting. 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 states a specific action ('Get users recently active in a chat room') with a clear resource and scope. It distinguishes itself from sibling tools like get_chat_messages by focusing on users rather than messages, and the @mention tip ties it to send_chat_message.

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 description explicitly tells how to use the returned usernames for @mentions in send_chat_message, implying a primary use case. However, it does not explicitly state when not to use this tool or mention alternatives like get_chat_messages for related needs.

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