Prebuilt vs declarative vs custom engine vs Foundry Agent Service vs Azure infrastructure

This sheet compares Prebuilt agent, Declarative agent, Custom engine agent, Foundry Agent Service, Azure infrastructure.

CriterionPrebuilt agentDeclarative agentCustom engine agentFoundry Agent ServiceAzure infrastructure
Who runs the stackMicrosoft and partners; no build effort and no separate hostingCopilot's AI infrastructure, model and orchestrator; no additional hostingUsually hosted outside Microsoft 365 (typically Azure) at extra cost, with your own orchestrator; Copilot Studio can also host one in Microsoft 365Microsoft runs the managed platform; no servers to maintain; model tokens and compute are chargedYour own runtime and models on compute you manage; the most build and maintenance effort

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