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umbra

umbra

by lxchx
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

Close

close

Terminates a browser tab while keeping the browser open, freeing memory after one-off tasks.

Instructions

Close a tab. Browser stays for other tabs. Free RAM after one-off tasks.

Ex: close('t0') → {"closed":true}

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": {
      "tab_id": "<tab_id>"
    },
    "name": "close"
  }
}

Input Schema

NameRequiredDescriptionDefault
tab_idYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4.1/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and does well: it discloses that the browser survives, other tabs are unaffected, and memory is reclaimed. It omits behavior for an invalid or already-closed tab_id (error vs. idempotent no-op), which is the main remaining gap for a mutation.

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?

Three short fragments plus an example, with the core action and its contrast front-loaded and zero filler. Every sentence adds information the agent needs.

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?

An output schema exists, so the return value needn't be explained (it is shown anyway), and for a one-parameter tab-scoped tool this is nearly complete. The only missing piece is where to obtain a valid tab_id and how failures are reported.

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 0% and the single parameter is undocumented, but the worked example close('t0') → {"closed":true} reveals the tab_id format and where such identifiers come from (list_tabs). That compensates for the missing schema description, though it stops short of stating whether the id must come from list_tabs.

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 ('Close a tab') and immediately distinguishes scope from the browser-level siblings by noting 'Browser stays for other tabs' — implicitly contrasting with close_browser and kill_all. It does not name those siblings explicitly, so differentiation is inferential rather than stated.

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?

'Free RAM after one-off tasks' gives a concrete when-to-use context, and 'Browser stays for other tabs' signals when this is preferable to a full browser teardown. There are no explicit exclusions or named alternatives, keeping it short of a 5.

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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