def valid_links(links):
    """Determines validity of input link JSON.

    JSON must have a single entry 'links' which contains a list of strings.

    :param links: Dictionary representing input JSON
    :returns: True if valid, False if not
    :rtype: boolean

    """
    if type(links) is not dict:
        return False
    if len(links) is not 1:
        return False
    if 'links' not in links:
        return False
    if type(links['links']) is not list:
        return False
    if not list or not all(isinstance(s, str) for s in links['links']):
        return False
    return True