I have been trying to figure out how to use this client, namely client.bulk but there is no docs to even explain what the parameters should be. Any help would be appreciated.
There is a sparsity of example code for this client.
The opensearch-js client was forked from elasticsearch-js. Therefore bulk examples from older versions of the elasticsearch javascript client should work.
If you are interested in contributing, feel free to propose some documentation improvements, starting with opening an issue in the opensearch-js repo.