Create a transaction request for signing an off-chain message with your keys for an MPC wallet. Use this endpoint when you need to produce a cryptographic signature over arbitrary data without broadcasting a transaction on-chain. Common use cases include proving wallet ownership to a dApp, signing authentication challenges, and signing EIP-191 or EIP-712 typed data.

Use only for MPC wallets. Supported chains include EVM-compatible chains (ETH, BSC, Polygon, etc.), Solana, and Cardano. UTXO-based chains (Bitcoin, Litecoin, etc.) are not supported.

To execute on-chain transactions with custom instructions (such as signing an on-chain message), use Create transaction request.