agentWallet + agentId pair before agent work. linked: true means matching agent-identity and agent-delegation proofs were found. If either is missing, you get link_required, missingVerifiers, and a hosted URL for only the remaining step.
agentId is optional only when the wallet identifies one agent unambiguously. Pass it whenever a wallet hosts several agents. Optional principal hints the controller account (not the agent wallet). Agent concepts
When you need prepared signing payloads first, see Agent create.