It completely depends on the manual. If this is the first time I have ever seen it, and it's about something I have never used, it very well might take me a while to figure out how to look up information quickly and effectively.

Does the manual having working code examples? Then is it probably a good manual. If it does not have working examples that you can copy & paste (and they actually work), then it probably is terrible.

There is enormous variation in the quality of different indexes (indices?) The whole concept of an index, at least since computers have been around, should be that it's better than a full text search, but that's not something you can automatically generate.