When MCP Agents Break Production: Failure Patterns from 20,000 Tool Invocations

MCP Dev Summit Toronto 2026

Oct 5, 2026 · 11:30–11:55 · Timezone not confirmed

We deployed an MCP agent to investigate seller support issues across 8 AWS accounts. In its first month: 20,000+ tool invocations, investigation time reduced from 10 minutes to 30 seconds. Then a single input validation regex in our tool pipeline silently zeroed inventory for 70+ sellers — a Sev-2 incident caused by the system designed to protect them. This talk covers three production failure patterns unique to multi-tool MCP architectures: (1) Validation boundary mismatches - when tool-level schemas disagree with upstream data formats, creating silent data corruption. (2) Credential scoping in multi-account routing - how we handle 8 AWS accounts with one agent session without cross-tenant leakage. (3) Observability gaps at the transport layer - why our agent's reasoning traces missed the failure (it happened in API Gateway VTL, outside the MCP tool boundary) and the anomaly detection patterns we now enforce. Built with MCP's open protocol, running against Bedrock. No vendor pitch - just patterns, anti-patterns, and the three rules we'd enforce from day one if we started over.

Session status: scheduled

Room: Giovanni

Track: Agent Architecture + Orchestration

Level: Intermediate

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In person · The Conference Centre at the University of Toronto, Toronto, Ontario, Canada

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