How can I manipulate the output of Information?

You may use the "PlaintextUsage" or "TypesetUsage"property of WolframLanguageData.

WolframLanguageData["ProductLog", "PlaintextUsage"]

WolframLanguageData[ToString@ProductLog, "PlaintextUsage"]

gives

"ProductLog[z] gives the principal solution for w in z\[LongEqual]we^w. ProductLog[k, z] gives the k^th solution."

Note the escapes like "\[LongEqual]" will evaluate to their symbol in strings in Mathematica/Wolfram Language.

For typeset lines then

WolframLanguageData["ProductLog", "TypesetUsage"][[1, 1]]

Hope this helps.

A simpler method to get the usage messages for further manipulation is to use MessageName[symbol, "usage"]:

MessageName[ProductLog, "usage"]

which already yields a typeset version, similar to what is produced by Information[].

And of course, Attributes[symbol] will return symbol's associated attributes.

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