session_listLists all open isolated browser sessions, including each session's mode, tabs, and whether it is busy, so you can monitor and manage parallel browser work.
List open sessions with their mode, tabs and whether they are busy.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and scope are covered. The description adds useful return context by naming mode, tabs, and busy status, though it omits ordering or pagination behavior.
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 efficient sentence with the main purpose and returned fields front-loaded. Every phrase earns its place.
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 zero-parameter read-only listing tool, the description plus annotations provide enough context to call it correctly. Although there is no output schema, the description names the key returned attributes.
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 there are no parameter semantics to explain; baseline 4 applies. Schema description coverage is 100%, leaving nothing ambiguous for the agent to supply.
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 gives a specific verb/resource (List open sessions) and states the returned attributes (mode, tabs, busy). It is clear what the tool does, though it does not explicitly differentiate itself from session_create or session_close.
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?
There is no explicit guidance on when to use this tool versus alternatives, nor any exclusions or prerequisites. The usage is only implied by the name and one-line description.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.