/** Base error class for InvoiceFlow MCP operations. Contains user-friendly message and error code. */
export declare class InvoiceFlowError extends Error {
    readonly userMessage: string;
    readonly code: string;
    constructor(message: string, userMessage: string, code: string);
}
/** Thrown when a requested entity (lead, invoice, campaign, etc.) is not found by ID. */
export declare class NotFoundError extends InvoiceFlowError {
    constructor(entity: string, id: string);
}
/** Thrown when attempting to create a duplicate entity. */
export declare class DuplicateError extends InvoiceFlowError {
    constructor(field: string, value: string);
}
/** Thrown when input validation fails (invalid UUID, out-of-range values, etc.). */
export declare class ValidationError extends InvoiceFlowError {
    constructor(details: string);
}
export declare const RE_UUID: RegExp;
/** Validates that a string is a valid UUID v4 format. Throws ValidationError if invalid. */
export declare function validateUUID(id: string, entity: string): void;
/** Converts any error into a standardized MCP tool error response with user-friendly message. */
export declare function handleToolError(error: unknown): {
    content: {
        type: 'text';
        text: string;
    }[];
    isError: true;
};