For most business software problems, there are now three viable paths: build a custom solution, buy an off-the-shelf product, or deploy an AI agent. Each has a distinct profile of cost, risk, and fit. Here is how to think about the choice.
When to buy
Buy when your need is generic. If hundreds of businesses have the same problem and there are established products solving it — accounting, CRM, HR management, project management — buying is almost always the right answer. The product has been tested by thousands of users, the bugs have been found, and the vendor is investing in improvements continuously.
The signal that you should buy: you are describing your need in terms that match the marketing copy of an existing product.
When to build
Build when your need is genuinely differentiated — when the thing you are building is itself a competitive advantage, or when no existing product fits without significant compromise. Building is expensive and slow, but it produces something you own and can shape entirely.
The signal that you should build: your need is core to your product and unique enough that existing tools would require so much customisation that you are effectively building anyway.
When to deploy an agent
Deploy an agent when your need is a repeating workflow — not a product, but a process. Data entry, document processing, customer communication triage, internal request routing. Agents are strong at taking a well-defined process and running it at scale without the overhead of a full software build.
The signal that you should deploy an agent: you can describe the process as a series of steps that a reasonably capable human could follow given clear instructions.
The hybrid reality
Most businesses end up with a combination. Buy the category tools (CRM, accounting, project management). Build the things that are genuinely differentiating. Deploy agents for the high-volume repetitive processes that neither category addresses well. The frameworks are not mutually exclusive — they apply to different problems within the same organisation.