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zen-browser

zen-browser

by grapedjuice
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

tabs_close

Close a specified tab by tab ID to remove unwanted or completed tabs from the current Zen or Firefox browser session.

Instructions

Close a 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": "tabs_close"
  }
}

Input Schema

NameRequiredDescriptionDefault
tabIdYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

C2.4/5.0
Behavior2/5

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

No annotations and no output schema are provided, so the description carries the full burden of behavioral disclosure and does essentially none of it. It does not say what happens to unsaved page state, whether closing the last tab closes the window, or what occurs if tabId is invalid or refers to an already-closed tab.

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

Conciseness3/5

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

Three words, front-loaded, nothing redundant - but that brevity comes at the cost of under-specification rather than efficiency. There is no second sentence that would earn its place by clarifying scope or side effects.

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?

For a single-parameter mutation tool, the definition should at minimum explain how to source a tab id and what side effects to expect, since no annotations or output schema cover either. The description provides neither, leaving the agent to guess before an irreversible action.

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?

Schema description coverage is 0%, so the single tabId parameter is undocumented anywhere, and the description does not compensate at all - it never mentions tabId, how to obtain a valid id (e.g., via tabs_context), or why the schema accepts negative integers. Only the parameter name hints at its meaning.

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

Purpose3/5

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

"Close a tab" names a verb and a resource, so the basic operation is unambiguous, but it effectively restates the tool name tabs_close and adds no scope information. It leaves open which tab is targeted (active tab vs. a background tab by id) and does not distinguish the operation from siblings like tabs_select or tabs_create.

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 when-to-use guidance, no preconditions (must the tab be selected/active first?), and no reference to an alternative tool. An agent has to infer from the name alone that this is the removal counterpart to tabs_create.

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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