I am posting an answer regarding this specific aspect, so that it's easier to comment (and vote) on this specific issue. (Basically summarizing some stuff already mentioned in the comments.) To add some context I will explicitly mention that the question originally suggested tag for cyclic sums.
Proposal: If a tag for this type of sums is created, it would be better to have both cyclic sums and symmetric sums under the same tag rather than a tag just for cyclic sums. (Perhaps the tag could be called something like cyclic-symmetric-sums or cyclic-and-symmetric-sums.)
Some relevant points:
- These two types of sum are - to some extent - related.
- I'd say that it's not unusual to have problems where both cyclic and symmetric sums occur. In such case, two tags might be relevant for the question. Having only five slots available for tags, taking up two slots by closely related tags might cause problems for having questions correctly tagged.
As far as I can tell, many questions about symmetric sums are now tagged using the symmetric-polynomials tag. (If you check questions tagged or symmetric-polynomials+summation, symmetric-polynomials+inequality or symmetric-polynomials+contest-math you can find plenty of such questions. In some cases it's possible that this tag is not really suitable and the tag for cyclic sums would be a better fit.
Of course, symmetric sum is not always a symmetric polynomial, but typically it is closely related to some symmetric polynomials. (For example, cyclic sums appearing in some problems can be rewritten as a fraction in such a way that both numerator and denominator are symmetric polynomials.)
Close relation to the existing tag symmetric-polynomials and existing usage suggest some potential problems:
- Sometimes it might be unclear whether it's better to use the tag for symmetric polynomials or the tag for symmetric (and cyclic) sum. (I'd guess that a reasonable rule of thumb might be that the tag about symmetric sums is intended mostly for questions related to contest math.)
- Since in the past the tag (symmetric-polynomials) was used in this context, probably a non-negligible number of questions might need retagging.
Despite the potential problems I think that having a single tag (cyclic-and-symmetric-sums) to use for some contest question might be better solution than to add to such question, for example, the three tags (cyclic-sums), (summation) and (symmetric-polynomials). (If they are applicable.)