browser_list_sessions

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

With no annotations, the description carries the full burden. It discloses that 'Dead sessions are automatically cleaned up,' which is a useful behavioral trait beyond the obvious 'list' action. It also specifies the returned fields (status, PID, ports, uptime), giving transparency into the output. It doesn't explicitly state that the operation is read-only, but that is reasonably implied by the verb and context.

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 short sentences, front-loaded with the core action and immediately followed by a usage hint and a behavioral note. Every word earns its place; there is no fluff or repetition. This is model of conciseness.

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 list operation with no parameters, the description covers purpose, usage timing, return fields, and a non-obvious behavior (auto-cleanup of dead sessions). An output schema exists to detail the return structure further, so the description is complete enough for an agent to select and invoke the tool 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 tool has zero parameters, so the input schema is trivially covered (100% by default). The description mentions the output fields even though an output schema exists, adding semantic value about what the returned data looks like. This aligns with the baseline of 4 for zero-parameter 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 begins with 'List all active browser sessions' – a specific verb and resource – and elaborates with status, PID, ports, and uptime. This clearly distinguishes it from sibling tools like browser_list_tabs (which lists tabs within a session) and browser_close (which affects sessions). The purpose is unambiguous.

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?

It explicitly advises 'Use this to check which sessions are running before sending commands,' providing clear context for when to invoke this tool. It doesn't mention exclusions or alternatives by name, but the usage hint makes the appropriate scenario evident. Sibling differentiation is implicit rather than explicit.

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