One Million Tools

css_contrast_check

Compute the WCAG contrast ratio between two colors and the AA/AAA verdict.

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": {
      "foreground": "<foreground>",
      "background": "<background>"
    },
    "name": "css_contrast_check"
  }
}

Input Schema

Name	Required	Description	Default
`background`	Yes
`foreground`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 21, 2026

TDQS

B3.3/5.0

Behavior3/5

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

With no annotations, the description carries the full burden. It usefully discloses the evaluation standard (WCAG) and that a pass/fail verdict (AA/AAA) is produced, implying a pure, side-effect-free computation. However it omits the accepted color input formats and any assumptions about transparency/alpha, which are the main behavioral unknowns for this tool.

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?

A single front-loaded sentence stating operation, standard, and result. Nothing is wasted and nothing is buried.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, but the description does summarize the return (ratio plus AA/AAA verdict), which covers the essentials. The unresolved gap is input color-format handling, which an agent needs before it can call this reliably.

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 description must compensate. It only implicitly names the two inputs via 'between two colors'; the schema's 'foreground'/'background' names are self-evident, but no accepted format (hex, rgb(), named, alpha) is documented anywhere, leaving real ambiguity.

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?

The description gives a specific verb and resource ('Compute the WCAG contrast ratio between two colors') plus the output artifact ('AA/AAA verdict'), which is more than a tautology. It does not name or contrast itself against any sibling (e.g. color_convert), so it stops short of full sibling differentiation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied rather than stated: an agent can infer this is the accessibility-contrast tool as opposed to the general color_convert sibling. There is no explicit when-to-use/when-not guidance and no mention of alternatives.

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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