/**
 * Represents a Tag value object in a TlvEntity structure.
 *
 * This class encapsulates the tag identifier ensuring that it complies with the expected format.
 * According to the EMVCo specifications, a valid Tag is typically a two-character string.
 */
export declare class Tag {
    private readonly _value;
    /**
     * Constructs a Tag value object.
     *
     * @param value - The tag string. It must be exactly two characters.
     * @throws {Error} If the tag is not exactly two characters.
     */
    constructor(value: string);
    /**
     * Returns the tag value as a string.
     *
     * @returns The tag as a string.
     */
    toString(): string;
    /**
     * Validates the provided tag value.
     *
     * @param value - The tag value to validate.
     * @returns True if the tag is exactly two characters, false otherwise.
     */
    static isValid(value: string): boolean;
}