In this lecture, we break down how to “painlessly” embed a ChatGPT App into an existing product: we treat MCP as a thin adapter/gateway over REST/GraphQL and domain services, build a single source of truth for schemas (e.g., via Zod), design contract tests, plan versioning for
tools/
resources, and run zero‑downtime migrations. We also discuss the evolution of the OAuth layer (including
/.well-known/oauth-protected-resource,
scopes, and
WWW-Authenticate), the hint layer of metadata/annotations (
readOnlyHint,
destructiveHint,
openWorldHint), as well as SDK upgrade processes and common mistakes that lead to runtime incidents and quality degradation.