Choosing deterministic vs agentic architecture

The default should be the deterministic pipeline, not the agent. A fixed sequence of steps is cheaper to run, trivially easier to test (the same input always produces the same path through the code), and far easier to reason about when something goes wrong in production. An agentic loop earns its place only when the task's branching is too open-ended to enumerate: the set of possible next actions depends on what was just discovered, not on a fixed decision tree drawn up front.

When agents do talk to other systems or to each other, the protocol matters. Model Context Protocol (MCP) standardizes how a single agent connects to tools, giving it a consistent interface instead of a bespoke integration per tool. Agent-to-Agent protocols (A2A) sit at a different layer, coordinating multiple agents rather than one agent's tool access -- the two are complementary, not competing standards, and most non-trivial multi-agent systems eventually need both.