# Create an onramp transaction

Initiates a Coinbase onramp flow for purchasing crypto with fiat

Endpoint: POST /v1/defi/core/onramp
Version: v2026_01_14
Security: bearerAuth

## Request fields (application/json):

  - `chain` (string, required)
    The blockchain to onramp to (e.g., "solana", "base")
    Enum: "solana", "base"

  - `amount` (string, required)
    The amount to purchase in USD

  - `payment_method` (string, required)
    The payment method to use

## Response 200 fields (application/json):

  - `url` (string)
    The Coinbase onramp URL to redirect the user to

  - `tx_id` (string)
    The transaction ID for tracking

## Response 400 fields (application/json):

  - `message` (string)

## Response 401 fields (application/json):

  - `message` (string)

## Response 404 fields (application/json):

  - `message` (string)

## Response 500 fields (application/json):

  - `message` (string)