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Fast Browser MCP

Fast Browser MCP

by kqlio67
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

browser_set_media_theme

Set the page's preferred color scheme (dark, light, or no-preference) to emulate system theme and test responsive designs.

Instructions

Emulate system color scheme on page: 'dark', 'light', or 'no-preference'.

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": {
      "theme": "<theme>"
    },
    "name": "browser_set_media_theme"
  }
}

Input Schema

NameRequiredDescriptionDefault
themeYesdark

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.8.0

TDQS

C2.9/5.0
Behavior2/5

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

With no annotations, the description carries full behavioral burden. It never states whether the emulation applies to the current tab or all tabs, whether it persists across navigations, or how to revert it (e.g., setting 'no-preference'). This is a meaningful gap for a browser-state mutation.

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?

A single front-loaded sentence with no filler; the verb and allowed values come immediately. It is arguably too terse rather than verbose, but structure-wise it is clean.

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 simple one-parameter tool this is close to adequate, but with no annotations and no output schema the description should at least state scope (tab vs. browser-wide) and persistence/reversal behavior. Those omissions leave an agent guessing about side effects.

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 description coverage is 0%, but the single parameter is an enum whose values are self-documenting. The description restates those same three values rather than explaining the semantic effect of each (e.g., how 'no-preference' differs from clearing emulation), so it adds only marginal meaning beyond the 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 ('Emulate system color scheme on page') and enumerates the accepted values, so an agent knows exactly what changes. It is reasonably distinct from siblings like browser_emulate_environment or browser_set_viewport, though it doesn't explicitly contrast itself with them.

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 guidance on when to use this tool, no prerequisites, and no mention of alternatives such as browser_emulate_environment for broader emulation. The purpose is inferable (dark-mode testing), but nothing is stated.

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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