def gen_wtml(base_dir, depth, **kwargs):
    """
    Create a minimal WTML record for a pyramid generated by toasty

    Parameters
    ----------
    base_dir : str
      The base path to a toast pyramid, as you wish for it to appear
      in the WTML file (i.e., this should be a path visible to a server)
    depth : int
      The maximum depth of the pyramid

    Optional Keywords
    -----------------
    FolderName
    BandPass
    Name
    Credits
    CreditsUrl
    ThumbnailUrl

    Returns
    -------
    wtml : str
      A WTML record
    """
    kwargs.setdefault('FolderName', 'Toasty')
    kwargs.setdefault('BandPass', 'Visible')
    kwargs.setdefault('Name', 'Toasty map')
    kwargs.setdefault('Credits', 'Toasty')
    kwargs.setdefault('CreditsUrl', 'http://github.com/ChrisBeaumont/toasty')
    kwargs.setdefault('ThumbnailUrl', '')
    kwargs['url'] = base_dir
    kwargs['depth'] = depth
    template = """<Folder Name="{FolderName}">
<ImageSet Generic="False" DataSetType="Sky" BandPass="{BandPass}" Name="{Name}" Url="{url}/{{1}}/{{3}}/{{3}}_{{2}}.png" BaseTileLevel="0" TileLevels="{depth}" BaseDegreesPerTile="180" FileType=".png" BottomsUp="False" Projection="Toast" QuadTreeMap="" CenterX="0" CenterY="0" OffsetX="0" OffsetY="0" Rotation="0" Sparse="False" ElevationModel="False">
<Credits> {Credits} </Credits>
<CreditsUrl>{CreditsUrl}</CreditsUrl>
<ThumbnailUrl>{ThumbnailUrl}</ThumbnailUrl>
<Description/>
</ImageSet>
</Folder>"""
    return template.format(**kwargs)
