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set_color_scheme

Idempotent

Override the browser's color scheme to emulate light, dark, system, or no-preference modes for accurate color inspection and screenshots.

Instructions

Set the browser color scheme that controls CSS prefers-color-scheme. Defaults to system appearance. Use before inspecting colors or taking screenshots. Options: system (clear override to follow OS/browser setting), dark, light, no-preference (simulate agents with no declared preference). Returns confirmation of the active scheme.

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": {
      "scheme": "<scheme>"
    },
    "name": "set_color_scheme"
  }
}

Input Schema

Name	Required	Description	Default
`scheme`	Yes	Color scheme to emulate: 'system', 'dark', 'light', or 'no-preference'. Example: { scheme: 'dark' }

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.13.0May 11, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations indicate idempotentHint=true, and description adds that it defaults to system appearance and returns confirmation of the active scheme. No contradictions; provides useful context beyond annotations.

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 sentences with no redundant information. Front-loaded with purpose and usage, then details options and return value.

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?

Complete for this simple tool: purpose, when to use, parameter options explained, and return value stated. No output schema needed.

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 has 100% coverage with a description, but the tool description explains each option's effect (e.g., 'system (clear override to follow OS/browser setting)'), adding value beyond the schema.

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 clearly states the tool sets the browser color scheme for CSS prefers-color-scheme, lists all options, and distinguishes it from sibling tools which cover other browser automation tasks.

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?

Explicitly states 'Use before inspecting colors or taking screenshots', providing clear context. Does not mention when not to use or alternatives, but this is sufficient given the tool's specificity.

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