session_list

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

No annotations are provided, so the description carries the full burden. It compensates by disclosing the exact shape of the result (the fields and the active marker), effectively standing in for the missing output schema, and 'List' signals a non-mutating read. It stops short of stating whether the list can be empty or whether sessions from other clients are included.

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?

Two sentences, no filler. The what (list with field breakdown) is front-loaded and the routing guidance follows immediately, so an agent gets value from the first clause onward.

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 parameterless, read-only listing tool with no output schema and no annotations, the description covers the return shape and the intended follow-up actions. Nothing an agent needs to invoke it correctly is missing.

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, so there is nothing to disambiguate; baseline 4 applies. The description correctly adds no parameter guidance because none is possible.

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?

States a specific verb and resource ('List every open browser session') and enumerates exactly what each entry contains (id, browser, headless, window size, start time, active flag). This cleanly separates it from the session_create/session_select/session_destroy siblings, which mutate rather than enumerate.

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?

Explicitly names the downstream alternatives and the condition that selects them: use this to find ids for session_select or session_destroy, or to check what is still running. The agent does not have to infer when this tool is the right entry point.

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