# check_color_contrast

Check WCAG contrast ratio between two colors for accessibility.

Agent View of the PolicyLayer registry record for `check_color_contrast`. HTML page: https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/check-color-contrast

## Facts

- Tool: `check_color_contrast`
- Server: GadgetHumans API Hub (`pypi:gadgethumans-api-hub-mcp`) — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub.md
- Install: `npx -y pypi:gadgethumans-api-hub-mcp`
- Homepage: https://github.com/scotia1973-bot/api-hub
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "check_color_contrast",
    "arguments": {}
  }
}
```

## Why check_color_contrast is rated Low

The tool analyzes and returns accessibility data (contrast ratio values) based on input parameters. It has no side effects, does not create or modify data, does not execute code or commands, and does not involve financial or destructive operations. This is a pure utility function for accessibility compliance checking, clearly fitting the Read category.

From the tool's own definition: "Tool 'check_color_contrast' performs a contrast ratio calculation between two colors according to WCAG standards. This is a read-only operation that retrieves or computes accessibility metrics without modifying, deleting, or executing arbitrary operations."

## Use case

AI agents call check_color_contrast to retrieve information from GadgetHumans API Hub without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches GadgetHumans API Hub:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "check_color_contrast": {}
  }
}
```

## Other tools on GadgetHumans API Hub (310)

- `clean_whitespace` — Destructive — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/clean-whitespace.md
- `gravitational_force_calc` — Destructive — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/gravitational-force-calc.md
- `atbash_cipher` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/atbash-cipher.md
- `caesar_cipher` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/caesar-cipher.md
- `crawl_website` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/crawl-website.md
- `electrical_calc` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/electrical-calc.md
- `evaluate_math` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/evaluate-math.md
- `filter_data` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/filter-data.md
- `fn` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/fn.md
- `generate_password` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/generate-password.md
- `hash_text` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/hash-text.md
- `http_client` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/http-client.md
- `ini_to_json` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/ini-to-json.md
- `matrix_operations` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/matrix-operations.md
- `momentum_calc` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/momentum-calc.md
- `pressure_calc` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/pressure-calc.md
- `ratio_calc` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/ratio-calc.md
- `test_regex` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/test-regex.md
- `web_scrape` — Execute — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/web-scrape.md
- `agent_memory` — Other — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/agent-memory.md
- `generate_ulids` — Other — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/generate-ulids.md
- `alternating_case` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/alternating-case.md
- `amortization_calc` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/amortization-calc.md
- `anagram_check` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/anagram-check.md
- `analyze_tone` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/analyze-tone.md
- `analyze_url` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/analyze-url.md
- `angle_convert` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/angle-convert.md
- `area_convert` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/area-convert.md
- `ascii_table` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/ascii-table.md
- `auto_loan_calc` — Read — https://policylayer.com/tools/io-github-scotia1973-bot-api-hub/auto-loan-calc.md
- …and 280 more: https://policylayer.com/tools/io-github-scotia1973-bot-api-hub.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-scotia1973-bot-api-hub · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-scotia1973-bot-api-hub