Architecture Pattern: Using MCP as a Secure Middleware for 4-Phase Agent Workflows

[preet7777777]

www.linkedin.com/in/preet-sirohi-467913257

"I’ve been developing a Tech Support AI system using FastAPI and the Model Context Protocol. While the connectivity to tools like Jira, SMTP, and SSH is straightforward, scaling it for internal company use required a more robust 'Gateway' pattern.My Current Stack:Backend: FastAPI (port 8081)Gateway: MCP Hub (port 8000) managing f40115bd (Gmail), 28e07cd6 (Jira), and eb4c9a45 (Postgres).Pipeline: A 4-phase sequence (Classifier -> KB -> Investigator -> Synthesizer).The Challenge I Solved:To prevent unauthorized actions, I built an intermediary PII Engine and Role-validation layer between the Agent and the MCP tools. The agent requests a 'Write' action, but the Gateway validates the user's JWT/Role before executing the tool call.I’m looking for feedback on this 'Gatekeeper' pattern. Is it better to handle RBAC at the Agent level or as a middleware within the MCP server itself? I’ve found the middleware approach much cleaner for auditing."