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"
    }
  }
}

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

Tool	Method	Path	Price	Description
utility_convert_units	POST	/api/convert	$0.003	Convert a value between measurement units

utility_convert_units

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

Parameters

Name	Type	Required	Description
value	number	yes	The numeric value to convert
from	string	yes	Source unit (e.g. km, lb, celsius, l, mph, MB)
to	string	yes	Target unit (e.g. mi, kg, fahrenheit, gal, km/h, GB)
category	string	no	Optional category hint: length, weight, temperature, volume, speed, data

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