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Rust
Local

Adopt user's tab

browser_use_tab
Idempotent

Preserve signed-in or in-progress browser state by taking over an existing tab instead of opening a new one. Locate the tab with browser_list_tabs all=true, then continue working there.

Instructions

Take over a tab the user already has open, instead of opening a new one. Use this when the page is already signed in or mid-flow — a checkout, a draft, a dashboard behind SSO — and re-opening the URL would lose that state. Find the tab_id with browser_list_tabs all=true. The tab stays exactly where it is in the user's window; it is not moved into the agent's group, not activated, and not reloaded. It is never closed by cleanup — call browser_release_tab to hand it back. Ask the user before taking over a tab they are actively working in.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tab_idYestab_id of the user's tab, from browser_list_tabs all=true
session_idNoStable task or thread ID. Pass the same value on every browser call for this task. Different IDs isolate tabs and cleanup within one MCP process. Omit for the default process session.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.4.3
    • addedInput schema / properties / session_id
      Added value: +{
+  "description": "Stable task or thread ID. Pass the same value on every browser call for this task. Different IDs isolate tabs and cleanup within one MCP process. Omit for the default process session.",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}
  2. Changed1 schema field changedv0.3.1
    • changedInput schema / properties / tab_id / description
      Previous value: -"From browser_list_tabs all=true"New value: +"tab_id of the user's tab, from browser_list_tabs all=true"
  3. First observedv0.3.0

TDQS

A4.6/5.0
Behavior5/5

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

Annotations only declare readOnlyHint=false and destructiveHint=false. The description adds substantial behavioral context: the tab stays in the user's window, is not moved, activated, or reloaded, is never closed by cleanup, and requires browser_release_tab to hand it back. This goes well beyond what annotations convey and is consistent with them.

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

Conciseness4/5

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

Well-structured: purpose, usage, behavior, and handoff are presented in a logical order. The description is slightly verbose but each sentence adds essential information—no redundancy. Could be trimmed slightly, but it's highly efficient.

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?

For a tool that adopts a user's tab, the description covers the crucial context: when to use it, how to obtain the tab ID, the exact behavioral guarantees (no movement/reload), and the required release step. It also covers the safety aspect of asking the user. No missing information for an agent to call it correctly.

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

Parameters3/5

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

Schema description coverage is 100% for both parameters. The description repeats the tab_id source (from browser_list_tabs) but does not add new semantic meaning beyond what the schema already states. Baseline 3 is appropriate since the schema fully documents parameters.

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?

Clearly states the action: 'take over a tab the user already has open' rather than opening a new one. Distinguishes from siblings like browser_open_tab and browser_select_tab by specifying the unique behavior of adopting an existing tab.

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

Usage Guidelines5/5

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

Explicitly says when to use: when page is signed in or mid-flow and re-opening would lose state. Provides the concrete step to find the tab_id via browser_list_tabs all=true. Also instructs to ask the user before taking over an active tab, which is a key usage constraint.

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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