Agentic retrieval

"Can the buyer keep a dog at Flat 4?" No single chunk answers it. The lease's regulations schedule says no animals without the landlord's consent. Whether consent can be unreasonably withheld depends on the wording of a clause elsewhere in the lease, possibly varied by a later deed. Whether consent has already been given for this flat is in the replies to the leasehold enquiries, or in the managing agent's pack. A single search for "dog" finds the first piece at best. A conveyancer would read one thing, decide what to look for next, and keep going until they could answer. Agentic retrieval gives the agent the same ability: search is a tool it calls, as many times as it needs, with queries it writes based on what it has just read.

Context engineering introduced the idea of just-in-time retrieval: give the agent identifiers and tools rather than pre-loading documents. This lesson is about engineering that retrieval layer: which tools, how they return results, when grep beats an index, how to handle multi-hop questions, and how to measure and bound the cost.