The recipe site's first plan let family members upload a recipe and have a server-side agent import it to the live site, with no deploy. I designed that agent in full. It ran on the Claude API's Tool Runner rather than the Agent SDK, since it needed ten custom tools and no filesystem or shell. Its only route to the network was one fetch tool with an SSRF guard, a size cap and a timeout. A human-in-the-loop tool paused it for questions only the owner could answer, and the existing import skill compiled into its prompt, so one rulebook drove both harnesses.
Partway through, I weighed the cost: family accounts, an upload UI, a review queue and its own API spend, to replace a step I already did well. I changed the plan. Family members now submit a Google Form shaped around what the import skill needs, and I run the skill myself.
Agent architecture judgement (runtime choice, least-privilege tools, human gates), and the discipline not to build it.