Unit Converter API

Convert between units -- length, weight, temperature, volume, speed, data storage. Formula included. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

{
  "mcpServers": {
    "unit-converter": {
      "url": "https://unit-converter.api.klymax402.com/mcp"
    }
  }
}

Related MCP server: ucon-mcp

Quickstart -- HTTP (x402)

curl -X POST "https://unit-converter.api.klymax402.com/api/convert" \
  -H "Content-Type: application/json" \
  -d '{"value":"1","from":"...","to":"..."}'
# -> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

utility_convert_units

Use this when you need to convert between measurement units. Returns the conversion result with formula in JSON.

Parameters

Example response:

{"inputValue":100,"from":"km","to":"mi","result":62.1371,"formula":"100 km * 0.621371 = 62.1371 mi","category":"length"}

When to use: unit conversions in calculations, data analysis, scientific computing, recipe scaling, and engineering applications.

Not for: currency conversion (use finance_convert_currency), timezone conversion (use utility_convert_timezone), stock prices (use finance_get_stock_price).

Example agent prompts

• "Convert between measurement units"

Payment

• Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key

• Network: Base L2 (eip155:8453)

• Asset: USDC

• Facilitator: Coinbase CDP (primary), PayAI (fallback)

• Also reachable via ATXP (OAuth-wrapped x402, RFC 9728 protected-resource metadata)

Part of klymax402

100 x402 micropayment APIs for AI agents -- one wallet, USDC on Base, zero signup.

• Catalog: https://klymax402.com/llms.txt

• Full API reference: https://klymax402.com/llms-full.txt

• Live stats: https://klymax402.com/stats

License

MIT