Five workflow patterns cover nearly every design: prompt chaining, routing, parallelization, orchestrator-workers, and evaluator-optimizer.
Anthropic reports that agents use about 4 times the tokens of a chat and multi-agent systems about 15 times, which turns 10,000 monthly tasks on Claude Sonnet 5.5 from about $130 into about $1,950.
Choose the simplest pattern that passes your evaluation set, and cap workers, tool calls, and dollars per run in code rather than in the prompt.