Tags are not a “must add”, if you want to add them if you feel like you will use them, add those, but if you want to add some info about observation it’s better to put annotations and observation fields.
Tags are really for your own use, so you can add as many or as few tags as you want. I’ll second what @fffffffff has already said, annotations and observation fields are more important from a data quality standpoint. For example, it is better to put “larva” as a life stage annotation for an observation of a caterpillar than it is to add a “caterpillar” tag, although you should certainly feel free to do both if you desire.
The vast majority of my observations do not have any tags. The only time I add tags is if I want to be able to filter my own observations by some qualifier for which an observation field or annotation are not suitable. As an example, if I want to be able to filter my observations by a certain trip, I may add a tag like “Roadtrip2022” so that I can easily find everything I observed on this hypothetical trip.
I almost never add tags to my observations. As others have said above, tags are a completely optional thing to add. The only time I add tags is to link “similar observation sets” for different observations of the same organism during various stages of its life.
I like using the Host Plant > Insert Plant Name tag to keep track of insects or pollinators on certain kinds of flowers or plants
Also, when I manage capturing an animal eating another animal (or plant), I like using the tag fields to gather this kind of info.
I think you’re using Observation Fields in both those cases. Tags are the free-form pieces of text you can associate with an observation. They’re really mostly just to give individual observers an easy way to categorize stuff.
Many of my photos are taken outside of the app and I use keywords in the photo metadata to make them more searchable on my own computer. When I’ve added a tag with a species or higher taxon like “lizard”, the uploader reads those keywords and matches it to a taxon so I don’t have to label the photos again in iNat. It also imports all of those keywords as tags.
I have a bunch of tags that were auto-imported from Flickr and are pretty useless on iNat, such as camera info/image dimensions. I just haven’t had time yet to go through and clean them all up. For new observations, I will often add a tag with specific location info (e.g. name of hiking trail) or event info (e.g. State Park Bioblitz).
I think of tags as being more personal than observation fields and a good place to put things that might be only useful for you but not others on iNat. Tags allow you to easily search for all the observations with that tag, so one question to ask may be: What do you want/need to search your observations for? You can share those links. (Hint: If someone else happens to have used the same tag and you only want to get your own observations, you can further limit the search by user name.)
Specific example: I went on a walk with my young niece who doesn’t have an iNat account and we made some observations together. I uploaded those with a specific tag so I can share an Explore URL with her so she can show all her friends at school what cool stuff we found.
At this point, I use tags for locations that may not otherwise be searchable on iNaturalist, like the names of parks and cities. There are many, many possibilities, though, because these are our own personal labels.
I seldom use tags, although I have been known to do so, for example, “Redwood Forest” for observations made in that habitat that I particularly like. But the question has inspired me – I am going to go back through my observations and add tags, not to all of them, but to the ones in other habitats or localities that I particularly favor.
I have also tagged all my observations of trees as “tree.” Because I like trees.
Yes – as you will discover if you decide to add a tag to someone else’s observation. The option isn’t even there, although you can see any tags that they have added.