The instinct, when building an agent brief, is to be generous: the more information you give it, the less it can get wrong. Research from Anthropic and from the team that introduced retrieval-augmented generation tells a different story. Supplying everything at once spreads the agent’s attention across material that is irrelevant to the task in front of it. The right move is to supply a small number of stable facts upfront and let the agent retrieve the relevant piece when the job actually calls for it.
What belongs in the standing brief
Some facts do not change from run to run. A filing convention is a good example: it tells the agent how to categorise every document it touches, so it must be present before the first document is opened. These standing facts are part of the agent’s context from the moment it starts. Leave them out and every run risks drift. They cost almost nothing to include because they are short, stable, and always relevant.
What should be retrieved on demand
Most facts are not like that. A supplier’s prior statement, last quarter’s totals, the line items from a specific invoice: these are relevant to one document, or one figure, not to the run as a whole. Loading all of them upfront means the agent must hold and reason across material it will never use for the current task. Anthropic’s guidance on reducing hallucinations makes this point directly: the agent should extract the relevant piece of text first, word for word, before it begins its reasoning, rather than working from a broad supply already loaded into its brief. The Lewis retrieval research frames the same principle: retrieve the relevant piece at the moment the job requires it, rather than relying on what was already there at the start.
The monthly documents run
In the monthly financial-document run, two facts illustrate the split clearly. The filing convention, which sets out how every document is to be categorised, is supplied upfront every month: it is short, it never changes mid-run, and every document depends on it. The prior supplier statement is different. It is only needed when a figure on a current invoice requires checking against last month’s amount. Supplying it upfront for every document in the run loads irrelevant detail into the agent’s context for the large majority of documents where it is never needed. The right design retrieves it only when the agent reaches a document that actually calls for the check.
How to make the distinction
Ask two questions about each fact you are considering. First: is it relevant to every document or task in this run, or only to some? If it applies to every one, it belongs upfront. Second: will the agent know which piece to retrieve, and can it access the right source when it needs to? If yes, leave that fact out of the standing brief and instruct the agent to retrieve it on demand. The result is a brief that stays lean: a small number of stable guidelines at the top, and a clear instruction to pull the specific detail when the task requires it.
The takeaway is precise: loading more does not make the agent more capable. It makes it less focused. Separate the facts that hold for every run from the facts that belong to specific moments within a run, and you give the agent the conditions it needs to attend to the right thing at the right time.