list_sessions

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

There are no annotations, so the description carries the full burden of behavioral disclosure. The word 'active' adds a slight qualification, but the description does not explain what constitutes an 'active' session, the shape of the returned data, or whether it is a safe read-only operation. This is minimal and leaves significant behavioral questions unanswered.

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, concise sentence that front-loads the core action and object. Every word is essential and there is no filler, making it highly efficient.

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 the tool's simplicity (0 params, no output schema), the description is minimally adequate but leaves out important details such as what fields are returned for each session and what happens if no sessions are active. For a complete picture, the tool would benefit from specifying return structure or edge cases, so it is not fully complete.

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 takes zero parameters, and the empty input schema fully defines this. Per the rubric, 0 params earns a baseline of 4. The description adds no parameter information, but none is needed since there are no arguments to explain.

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 uses a specific verb 'List' and clearly identifies the resource as 'active browser sessions'. It is unambiguous and distinguishable from sibling tools like create_session, switch_session, and close_session by focusing on listing rather than state changes.

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 provides no guidance on when to use this tool versus alternatives like nst_get_profiles or nst_get_browsers. While the purpose is clear, the absence of any contextual usage hints means a user might wonder whether to list sessions or browsers.

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