Neynar Farcaster User Registration

Use this endpoint when you need to programmatically create a new Farcaster user account — particularly for apps that onboard users to Farcaster at scale, managed account flows, or when building Farcaster-native applications that require user registration via Neynar's managed signer infrastructure.

• Username already taken — 409 conflict returned
• Invalid or missing Ethereum custody address — 400 bad request
• Farcaster network registration failure — 503 service unavailable
• Insufficient payment or x402 payment not processed — 402 payment required
• Rate limit exceeded — 429 too many requests
• Invalid API key or unauthorized — 401 unauthorized