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Close browser session

browser_close

Destructive

Close and discard an unneeded in-memory browser session, clearing its document and history while keeping persistent cookies. Specify a session ID to target that session; otherwise, the active session closes.

Instructions

Closes and permanently discards one in-memory browser session, including its current document and history; persistent profile cookies remain saved. Use it when that tab is no longer needed. session_id targets a specific session; if omitted, the active session is closed. Returns closed, or not_found without changing another session.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`session_id`	No	Optional browser tab/session identifier.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.3.5Sep 16, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "type": "object"
+}

First observedv1.3.2Sep 15, 2026

TDQS

A4.5/5.0

Behavior4/5

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

The description adds significant behavioral context beyond the destructiveHint=true annotation: it specifies that the session is permanently discarded, history is removed, but persistent cookies remain saved. It also discloses the return values ('closed', 'not_found') and guarantees no effect on other sessions, which is useful for the agent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, each earning its place: action, usage, and parameter behavior. The most critical information (destructive action) is front-loaded, and there is no redundancy or fluff.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description fully covers what the agent needs: the action, its effects (including cookies and history), parameter behavior, and return values. The output schema exists for additional detail, but nothing critical is missing. The tool is simple, and the description is complete for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% (session_id is described as 'Optional browser tab/session identifier'), but the description adds meaningful clarification: 'targets a specific session; if omitted, the active session is closed.' This explains the default behavior and parameter semantics beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb+resource: 'Closes and permanently discards one in-memory browser session', which clearly distinguishes it from siblings like browser_open or browser_navigate. The scope is precise (one session, including document and history), leaving no ambiguity about what the tool does.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides a clear usage condition: 'Use it when that tab is no longer needed.' It also explains the optional session_id behavior, which helps the agent decide whether to pass it. It doesn't explicitly name alternatives, but the operation is simple and the context of siblings (all navigation/control) makes the intended use obvious.

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

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