I thought of quickly writing one, but it doesn't have an API. Something like this would work well:

POST your query, e.g.: tar zcf - some-dir | ssh some-server "cd /; tar xvzf -"

Returns:

    [
        ["tar(1)": "explanatory text"],
        ["z": "explanatory text"],
        ["x": "explanatory text"],
        ["f file": "explanatory text"],
    ]

etc.