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One Spec, Ten SDKs, Zero Excuses: Conformance Testing MCP - Paul Carleton, Anthropic#

MCP Dev Summit North America 2026 digest Program Adjacent pick 2–3 April 2026

Abstract

Paul Carleton, Member of Technical Staff, Anthropic

  • Why: "Compatibility without coordination" is MCP's core promise; this is the testing infrastructure that keeps ten SDK implementations honest, and a good template for conformance testing any protocol.
  • What: MCP's conformance testing infrastructure: real SDK implementations (Python, TypeScript, C#, Go) run against scenarios exercising specific protocol interactions — OAuth flows, Client ID Metadata Documents, resource metadata discovery — with analysis of behavior and conformance; including what running it across SDKs found, how it changed spec development, and how it enables attack simulation and evidence-based SDK tiering (from abstract only).
  • How: Scenario-based behavioral conformance harness that runs actual SDKs, not paper checks against the spec.
  • Where applicable: Directly relevant to MCP implementation maintainers; the conformance-harness pattern generalizes to any multi-implementation protocol effort.