Always create the index before loading the collection in Milvus: create_collection, insert, create_index, load_collection, then search. Or pass index_params at creation time, which creates the index and loads automatically. Start with AUTOINDEX unless you have a specific reason to pick HNSW or IVF variants.

Context: Official docs (index selection): documents the gotcha that Milvus errors if you call load_collection before creating an index on the vector field. The correct order is create collection, insert, create index, then load, then search. Agents that load right after insert get an error about no index on the vector field.