browser.list_sessions

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

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint, so the description doesn't need to restate safety. It adds behavioral context by specifying that the tool returns 'one reference each' with a defined set of fields (id, name, status, live, current page, takeover URL) and that both live and persisted sessions are included. This goes beyond the bare read-only annotation, though it stops short of discussing edge cases like empty lists, ordering, or pagination.

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 zero filler. It front-loads the action and resource, packs the essential field list into a concise parenthetical, and then immediately points to the main alternative. Every word contributes value.

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 no-parameter, no-output-schema list tool, the description covers the core needs: what it lists (live and persisted sessions), what each entry contains, and where to get a fuller record. It is complete enough for an agent to execute the tool correctly. The only minor gaps are unspecified edge-case behaviors (e.g., empty result set, session ordering) and the exact meaning of 'current page' and 'takeover URL', but these are not critical for correct invocation.

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 is empty (0 parameters), so the baseline for this dimension is 4. The description adds no parameter-specific meaning because there are no parameters to explain, and the empty schema already communicates that no arguments are required. The description instead focuses on the output, which is appropriate for a no-argument tool.

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 resource ('live and persisted browser sessions'), names the exact reference fields, and contrasts itself with browser.get_session ('returns a full record'). This clearly distinguishes it from sibling tools like list_tabs or list_downloads without needing to inspect 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 explicitly names the key alternative (browser.get_session) and indicates the difference in return granularity: this tool returns one summary reference per session, while get_session provides a full record. An agent can infer when to use this list tool vs. the detail tool. The context of other sibling tools (create, close, fork) is also implicitly separated by the focus on listing.

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