usable-browser-agent-free

browser_select_tab

Selects a browser tab by its ID to make it the active tab, enabling further actions on that tab.

Instructions

Make a tab active by id (the agent acts on the active tab).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "tabId": "<tabId>"
    },
    "name": "browser_select_tab"
  }
}

Input Schema

Name	Required	Description	Default
`tabId`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.7.0Sep 9, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It only states the action without revealing side effects, error handling, or whether the operation is reversible. The description is minimal and does not clarify what happens if the tab id is invalid or if any state changes occur beyond activation.

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?

The description is a single, front-loaded sentence that conveys the core purpose efficiently. It adds a useful nuance about the agent's interaction with the active tab. It is appropriately sized for the tool's simplicity, though it could be slightly more informative.

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

Completeness2/5

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

Given the tool's simplicity, a minimal description might suffice, but it lacks essential context for an agent: how to find the tab id, what happens on failure, and whether any output is returned. The sibling browser_list_tabs is not referenced, and there is no output schema to fall back on. This is incomplete for reliable tool selection and invocation.

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

Parameters2/5

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

The schema has a single parameter, tabId, with zero description coverage. The description mentions 'by id' but does not explain what the id represents, how to obtain it, or its format. Since the schema coverage is 0%, the description should compensate, but it only weakly ties the parameter to the action.

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 clearly states the action ('Make a tab active') and the resource (tab by id), and adds the context that the agent then acts on the active tab, which differentiates it from tab creation/closing tools. This is a specific and unambiguous purpose.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus alternatives like browser_new_tab or browser_close_tab. It does not mention prerequisites (e.g., using browser_list_tabs to obtain an id) or exclude any scenarios, leaving the agent to infer usage.

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

Deploy Server