Yes you can do that, but you would be taking an optimistic approach to the document being available in the format you want.
This is fine if you protect your client by having it expect and handle request failures. A metadata request will always succeed and tell you which document types are available (PDF, XBRL, iXBRL etc). If you’re always looking for a PDF, then your user journey doesn’t care about other formats, however, if you’re exposing a choice of documents to a user, then you need to drive that from the metadata request so that you’re user is informed as to what document types are available. Taking the optimistic approach, you could fire off a metadata request only if your request for a PDF, for example, fails…
More types will be added over time, and the API design transparently offers the new types to you (and your users), making it possible to create a client that does not need to know about the available types, and therefore be future proof.
There is another query with a similar outcome:
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