What does an agent actually cost? Designing for token economics before you ship

Most agent demos skip the question: what does an agent actually cost to run? A REST call costs the same every time. An agent doesn't, since the same prompt varies with reasoning depth, tool calls, retries and context growth. We'll map what you really pay for in Microsoft Foundry beyond model tokens and then look at several architectural options for controlling spend.. plus when NOT to build an agent at all. Expect some live demos in AI Foundry portal, and you'll leave with a FinOps checklist. Find more events in Liverpool and more about our group at https://dotnetliverpool.org.uk