Authenticate with TronSave and create a server session. Returns `{ sessionId, walletAddress?, expiresAt }` — pass `sessionId` as the `mcp-session-id` header on every subsequent MCP request. `walletAddress` is set only for signature-mode logins. Two modes: (1) wallet signature (preferred for platform tools) — call this tool with `signature_timestamp` formatted as `<signature>_<timestamp>`, where `<signature>` must be produced client-side by signing the timestamp message; you may optionally call `tronsave_get_sign_message` to obtain a helper message/timestamp pair; (2) API key (internal tools) — pass `apiKey` (raw key, no prefix). Side effect: creates a new session on the server. Wallet signing must happen client-side; never send private keys to the server.
Connector