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Monetary amounts

Monetary amounts are integer cents.
Amounts are always integers, never strings or floats. Maximum precision is 2 decimal places (1 cent).
Integer cents apply to the REST API and SDKs. Tools on the hosted MCP server instead take decimal-string amounts with a required currency ("amount": "10.50", "currency": "USD"); the MCP server converts between the two encodings at the boundary.

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Currency codes

ISO 4217 three-letter uppercase codes. Natural accepts USD. Every request that takes currency accepts an omitted value as USD, except payment intents, which require it.

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Timestamps

ISO 8601 / RFC 3339, always UTC.
Timestamps are RFC 3339 with millisecond precision in UTC (the Z suffix); the API does not return local time offsets. Timestamps you send must be RFC 3339 with an explicit Z or offset; a timestamp without a zone is rejected with invalid_value.

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Phone numbers

E.164 international format: plus sign, country code, subscriber number.