D2 error - multiboard output cannot be written to stdout

[f8dca]

The following D2 sample diagram in kroki :

how does the cat go?: {
  link: layers.cat
}

layers: {
  cat: {
    meoowww
  }
}

generates this error: 400 err: failed to compile -: multiboard output cannot be written to stdout (exit code 1)