/**
 * Logging utility — writes to stderr only (required for STDIO MCP transport)
 */
import winston from "winston";
export declare const logger: winston.Logger;
/**
 * Log a completed tool invocation with structured fields.
 *
 * @param method     Tool name (e.g. "read_memory")
 * @param sessionId  Active session ID, or empty string if not applicable
 * @param durationMs Wall-clock time for the invocation in milliseconds
 * @param error      Error message if the invocation failed; omit on success
 */
export declare function logToolCall(method: string, sessionId: string, durationMs: number, error?: string): void;
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