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