WCAG 2.1 contrast ratio checker between two colors, payable via x402 on Base/USDC.
What it does
The AgentUtil Color Contrast endpoint (`/v1/contrast`) calculates the WCAG 2.1 contrast ratio between a foreground and background color pair. It accepts colors in multiple formats—hex, rgb(), hsl(), or CSS named colors—and returns the numeric contrast ratio along with boolean pass/fail results for WCAG AA and AAA compliance at both normal and large text sizes. This is useful for accessibility auditing, design-system validation, and automated UI testing.
The endpoint is part of the broader AgentUtil Color service, which also offers color conversion (`/v1/convert`), palette generation (`/v1/palette`), and color blending (`/v1/blend`). Pricing is listed in the OpenAPI spec as $0.001 per request via x402 on the Base chain using USDC, with a free tier of 10 requests per day per IP that requires no signup.
Note: During probing, the endpoint returned HTTP 400 (not the expected 402 payment challenge) on a POST without a body, and 404 on GET. This likely means the endpoint validates the request body before issuing a payment challenge, or the free tier was not yet exhausted. The service root returns HTTP 200 with a simple color-picker page, and a full OpenAPI 3.1.0 spec is available, so the service appears operational but liveness via x402 challenge could not be independently confirmed.
Capabilities
Use cases
- —Automated WCAG accessibility audits for web pages
- —Design system CI pipelines that enforce minimum contrast ratios
- —Agent-driven UI generation that validates text readability
- —Checking foreground/background color pairs during theme creation
- —Accessibility compliance reporting
Fit
Best for
- —Agents building or validating accessible UIs
- —Automated design-system linting
- —Quick WCAG AA/AAA pass/fail checks on color pairs
Not for
- —Full-page accessibility scanning (this checks individual color pairs only)
- —Color conversion or palette generation (use sibling endpoints /v1/convert and /v1/palette instead)
Quick start
curl -X POST https://color.agentutil.net/v1/contrast \
-H 'Content-Type: application/json' \
-d '{"foreground": "#000000", "background": "#ffffff"}'Example
Request
{
"background": "#ffffff",
"foreground": "#000000"
}Response
{
"ratio": 21,
"aa_large": true,
"aa_normal": true,
"aaa_large": true,
"aaa_normal": true,
"background": "#ffffff",
"foreground": "#000000"
}Endpoint
Quality
A complete OpenAPI 3.1.0 schema with request/response definitions and pricing metadata is available, but the x402 payment challenge was not captured (endpoint returned 400, not 402), no dedicated docs or pricing pages exist, and the example response is inferred from the schema rather than observed.
Warnings
- —x402 challenge not confirmed: POST returned 400 instead of expected 402; liveness via payment protocol unverified
- —No dedicated documentation pages found (/docs, /api, /pricing, /README all return 404)
- —Example response is inferred from OpenAPI schema, not from an actual API call
Citations
- —Endpoint calculates WCAG 2.1 contrast ratio between two colorshttps://color.agentutil.net
- —Accepts foreground and background in hex, rgb(), hsl(), or CSS named color formatshttps://color.agentutil.net
- —Returns ratio, aa_normal, aa_large, aaa_normal, aaa_large booleanshttps://color.agentutil.net
- —Pricing is $0.001 per request via x402 on Base chain using USDC, with a free tier of 10 requests/day/IPhttps://color.agentutil.net
- —POST to /v1/contrast returned HTTP 400 during probe, not 402https://color.agentutil.net/v1/contrast