MCP in production for FDE teams

Reference docs Model Context Protocol docs, Token-based auth hardening patterns, and OWASP API Security Top 10.

Why MCP matters to FDE work

MCP gives a consistent contract for tools/resources across model stacks. For FDE teams, this reduces “custom glue per customer” and improves portability between lab and enterprise environments.

Production architecture baseline

1. Tool boundary: each MCP server owns a coherent domain (CRM, tickets, analytics, internal docs).
2. Auth boundary: identity and token scope are enforced at server edge, not delegated to prompts.
3. Policy boundary: explicit allowlists for tools/actions by role and environment.
4. Observability boundary: request ids, latency, error class, and permission-denial telemetry.

Contract design rules

• Keep tool schemas strict and versioned.
• Prefer deterministic, side-effect-safe reads by default; isolate writes.
• Return machine-parseable errors with stable codes.
• Expose minimal data needed for the task (avoid over-broad payloads).

Auth & permission model

• Short-lived tokens, scoped per server/tool category.
• Server-side re-check of user/action authorization.
• No “prompt can grant access” paths.
• Audit log for every write or privileged read.

Rollout sequence that works

1. Start with one read-only MCP server and high-value queries.
2. Add synthetic + replay tests for top task flows.
3. Introduce write tools behind explicit approvals and policy checks.
4. Gate expansion by SLOs: failure rate, latency, policy violations.

Failure modes to pre-empt

• Schema drift between client expectations and server output.
• Token scope mismatch across multi-tenant contexts.
• High-latency “tool waterfalls” from over-fragmented server design.
• Silent partial failures without clear retry semantics.

Interview framing tip

In FDE interviews, MCP discussion scores when you connect it to delivery outcomes: faster integration, safer permissions, and fewer bespoke adapters per customer.

Practice that bridge in case/decomp and system design rounds.