# Search Infrastructure

> Embedding models, vector and keyword indexes, retrieval engines, rerankers, and evaluation tools behind dependable search for agents.

## Field notes

- [What should a search API return to an agent?](https://www.searchforagents.com/blog/what-should-a-search-api-return-to-an-agent) — Valyu, Exa, and Parallel return different combinations of links, passages, dates, and diagnostics. Here is the evidence contract an agent needs to build around their results.