List sessions

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

Annotations already convey readOnlyHint=true and openWorldHint=true, so the description's job is light. It adds useful context by specifying the exact data returned (current URL, age, idle time), which goes beyond the annotation flags and tells the agent what to expect from the call. No contradiction with annotations exists.

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?

One efficient sentence that front-loads the core action ('Lists open browser sessions') and follows with the concrete data fields. There is no filler, no repetition, and every word adds meaning. Ideal for an agent to quickly parse.

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 has no parameters, no output schema, and annotations cover safety and world-behavior, the description is largely sufficient. It could be slightly more explicit about the exact structure of the returned list (e.g., array of objects vs. formatted text), but for a read-only listing tool the missing detail is minor and the description provides the essential information an agent needs.

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 coverage is 100% (vacuously). Per the instructions, the baseline for 0-parameter tools is 4. The description does not need to explain parameters, and it does not waste space trying; it focuses on the output instead.

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 ('lists') and a clear resource ('open browser sessions') and enumerates the returned attributes (URL, age, idle time). It unambiguously distinguishes this from navigation, clicking, and other browser actions, so an agent can separate it from siblings like browser_snapshot or browser_start without opening their schemas.

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 clearly indicates the tool's function, making the use case for listing sessions implied. However, it does not explicitly state when to prefer this over alternatives (e.g., browser_snapshot for current page state) or provide any exclusions. Without explicit routing, an agent must infer its appropriate place among many browser tools, so it falls short of clear standalone guidance.

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