I have been a long time proponent of monoliths, but it seems like agents would be happier with smaller, more isolated services. The more isolated, the better. Contracts between the service components only. Then it can iterate internally as long as it satisfies the contract. If it needs to, it can version the contract and keep iterating.
However, our world is not that world. Your agents may be happy in their tiny walled kingdom of toil and ineffectiveness, but you and your users will not. Poorly drawn service boundaries will drag you down more than almost any other architectural mistake.
If there is one universal amongst organizations, its that they love walls and silos. Be wary of putting them up ahead of time, cuz tearing them down once established is nearly impossible.
> If there is one universal amongst organizations, its that they love walls and silos.
> Your agents may be happy in their tiny walled kingdom...
That would be the point of using contracts as boundaries so the agent can iterate more autonomously so long as it maintains the externally facing contract or version the contract if it needs to.