An "admin.cluster" based API, which for a given a search request URI returns back the shards and nodes that the search is going to execute on.

The search shards API is using the same index as search API, except it uses the _search_shards end point instead of _search. For example, the following command will return a list of nodes and shards that would be used to execute a search request on index twitter with routing march:

$ curl -XGET 'http://localhost:9200/twitter/tweet/_search_shards?routing=march'

Shards that this command returns are grouped by index and shard_id.