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zen-browser

zen-browser

by grapedjuice
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

tabs_create

Opens a new browser tab, optionally at a specified URL, activates it, and returns its tabId for immediate browsing or automation.

Instructions

Open a new tab (optionally at a URL) and make it active. Returns its tabId.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "tabs_create"
  }
}

Input Schema

NameRequiredDescriptionDefault
urlNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

B3.4/5.0
Behavior3/5

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

With no annotations, the description carries the full behavioral burden, and it does disclose the key side effect (the new tab is made active) and the return value (tabId). It says nothing about the loading lifecycle — whether it resolves before the page loads, what happens with an invalid or unreachable URL, or whether background creation is possible.

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?

Two short sentences, front-loaded with the action and followed by the return value. Nothing is redundant and nothing needs reordering.

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

Completeness4/5

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

For a one-optional-parameter tool with no output schema and no annotations, this covers the essentials: action, optionality, activation behavior, and return value. Only the error and load-timing behavior are left unstated, which is minor at this complexity.

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?

The single `url` parameter has no schema description, but the prose establishes that it is optional and that omitting it yields a blank or default tab. It does not clarify expected format (absolute vs relative), default scheme handling, or whether the URL is validated.

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

Purpose4/5

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

The description gives a specific verb and resource ("Open a new tab") plus the optional URL and the activation side effect, which implicitly distinguishes it from tabs_select and tabs_close. It never names a sibling, so the differentiation is inferable rather than explicit.

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 versus tabs_select (switch to an existing tab) or navigate (go to a URL in the current tab). The agent must infer the selection rule from the sibling names alone.

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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