_search/*/_auto_complete

Purpose

Gets completions, supporting an auto-complete.

Auto-complete

Gets completions, given a prefix.

POST _search/<index names>/_auto_complete
{
  "prefix": "bas"
}

Result:

[
 "based",
 "basis",
 "basismaatregelen",
 "basisregistratie",
 "basisschoolleerlingen"
]

Completions are specific for the indexes as specified.