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umbra

umbra

by lxchx
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

List Tabs

list_tabs

Retrieves all open browser tabs with their URL, title, and browser ID, enabling agents to inspect current browser state before acting.

Instructions

List open tabs w/ URL+title+browser_id. Cheap.

Ex: list_tabs() → {"tabs":[{"id":"t0","browser":"default","url":"https://...","title":"..."}]}

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": "list_tabs"
  }
}

Input Schema

NameRequiredDescriptionDefault

No arguments

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.6/5.0
Behavior3/5

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

With no annotations present, the description must carry the behavioral burden; it does disclose a cost characteristic ("Cheap") and shows a concrete response shape, which is useful. It does not state that the operation is read-only/non-mutating, or whether it spans all browsers or only the active one, both of which matter given the sibling set.

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?

Two lines, front-loaded with purpose and cost, no padding. The example response partially duplicates the existing output schema, which is minor redundancy rather than noise.

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?

A zero-parameter, non-destructive listing tool with an output schema needs little prose, and the description covers purpose, cost, and return shape. The only gap is whether the list is scoped to one browser or spans all open browsers, which affects interpretation of the browser_id field.

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?

The tool takes zero parameters, so the baseline is 4. The example call list_tabs() reinforces that no arguments are accepted, matching the empty schema.

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?

States a specific verb and resource (list open tabs) plus the three fields returned (URL, title, browser_id), so the agent knows exactly what comes back. It does not differentiate against nearby siblings like list_browsers or current_state, which could plausibly overlap.

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

Usage Guidelines3/5

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

The single word "Cheap." implies this is a low-cost call and hints it should be preferred as a cheap discovery step, but usage is only implied. There is no explicit when-to-use, when-not, or named alternative among the many sibling tools.

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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