Closes a browser tab using its stable page ID, optionally within a specified session. Use it to remove tabs you no longer need during browser automation.
Close a tab by stable page ID.
| Name | Required | Description | Default |
|---|---|---|---|
| pageId | Yes | ||
| sessionId | No | Defaults to the active session |
Changes observed during successful MCP inspections.
v2026.10.24Input schema / properties / sessionId / descriptionPrevious value: -"Optional session ID; defaults to this MCP client active session"New value: +"Defaults to the active session"v2026.8.14Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The destructiveHint annotation already flags this as a destructive operation, but the description adds nothing: it does not say whether closing the last tab ends the session, whether the tab's state is lost, or whether the close is immediate. For a destructive tool, the one-liner leaves the agent with no behavioral context beyond the annotation.
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?
A single front-loaded sentence with no filler and the key identifier named up front. It is efficient, though the terseness borders on under-specification rather than tight 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?
A destructive, session-affecting mutation with only a bare destructiveHint, no output schema, and a half-documented schema. The description says nothing about what is destroyed, what happens to the browsing session, or the result — far short of what an agent needs before firing a close.
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?
Schema coverage is 50% — pageId is undocumented in the schema, and the description contributes the useful qualifier "stable," hinting it is a durable identifier rather than a positional index. However, it does not say where to obtain a pageId, so the schema gap is only partly compensated.
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 ("Close a tab") plus the identifier used ("stable page ID"), which distinguishes it from nex_browser_close (whole browser) by resource scope. It never names that sibling explicitly, so differentiation is implied rather than stated.
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?
No guidance on when to close a tab versus disconnecting or closing the whole browser, and no note that the pageId should come from nex_browser_tab_list. Usage is only inferable from the verb.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.