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zen-browser

zen-browser

by grapedjuice
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

tabs_context

List tabs in the focused Zen window with tab ID, title, URL, and active state, or include all windows. Call first to get tab IDs for switching or navigation.

Instructions

List the tabs in the focused Zen window (tabId, title, URL, which is active). Call this first to get tab ids.

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_context"
  }
}

Input Schema

NameRequiredDescriptionDefault
all_windowsNoInclude tabs from every window.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

A4.3/5.0
Behavior3/5

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

No annotations are provided, so the description carries the full disclosure burden. "List" and the field enumeration make the read-only, side-effect-free nature clear, and the focused-window scope is a useful behavioral detail; however, nothing is said about ordering, whether the list can be empty, or whether every open window is visible.

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 with zero filler; the scope and returned fields are front-loaded and the call-ordering advice follows immediately.

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 one-parameter read tool with no output schema, the description compensates by naming the fields returned (tabId, title, URL, active). Nothing an agent needs in order to call it correctly and interpret the result is missing.

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 coverage is 100%, so the all_windows parameter is already documented, giving a baseline of 3. The description adds real meaning by establishing that the default scope is the focused window, which is the condition all_windows overrides.

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?

States a specific verb and resource ("List the tabs"), names the exact scope ("focused Zen window"), and enumerates the returned fields (tabId, title, URL, active). This clearly separates it from the tabs_create/tabs_close/tabs_select siblings, which mutate or select rather than enumerate.

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?

"Call this first to get tab ids" gives explicit sequencing guidance and explains why an agent would reach for this tool before the other tabs_* operations. It lacks an explicit when-not or a named alternative, but the ordering cue is concrete rather than implied.

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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