def _get_headers(url, decoders):
    """
    Return a dictionary of HTTP headers to use in the outgoing request.
    """
    accept_media_types = decoders[0].get_media_types()
    if '*/*' not in accept_media_types:
        accept_media_types.append('*/*')

    headers = {
        'accept': ', '.join(accept_media_types),
        'user-agent': 'coreapi'
    }

    return headers