Charlotte

charlotte_tab_open

Open a new browser tab and optionally navigate to a URL. The new tab becomes active.

Instructions

Open a new browser tab. Optionally navigate to a URL. The new tab becomes the active tab.

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": "charlotte_tab_open"
  }
}

Input Schema

Name	Required	Description	Default
`url`	No	URL to navigate to (default: blank page)

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.8.0Aug 10, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

removedInput schema / additionalProperties
```
Removed value: -false
```

First observedv0.6.3May 26, 2026

TDQS

A4.3/5.0

Behavior4/5

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

With no annotations, the description carries the full burden. It effectively discloses the key behavioral traits: a new tab is created, optional navigation occurs, and the new tab becomes active. For a simple tool, this is sufficient, though it could mention that the previous tab remains open.

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?

The description is two concise sentences, with key information front-loaded. Every word earns its place, avoiding unnecessary detail.

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 single-parameter tool with no output schema, the description fully covers the purpose and behavior. It is complete enough for an agent to select and invoke the tool correctly.

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?

Schema coverage is 100% with the url parameter already described as 'URL to navigate to (default: blank page)'. The description does not add significant new semantics beyond repeating the optionality, so baseline 3 is appropriate.

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?

The description uses a specific verb ('Open') and resource ('browser tab'), clearly stating the action. It also distinguishes itself from sibling tools like charlotte_tab_switch and charlotte_tab_close by focusing on opening a new tab.

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?

The description provides clear context: opens a new tab and optionally navigates to a URL, with the new tab becoming active. However, it does not explicitly mention when to use this tool instead of charlotte_navigate (which likely navigates the current tab), leaving a slight gap in alternative guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.