Catalog of MCP server architecture patterns

Category: Paper
Status: developing
Sources: arXiv 2606.30317
Summary: A preprint posted 2026-06-29 catalogs five recurring architecture patterns for Model Context Protocol servers (Resource Gateway, Tool Orchestrator, Stateful Session Server, Proxy Aggregator, and Domain-Specific Adapter), plus four anti-patterns and cross-cutting concerns around authentication, versioning, and observability. The patterns are drawn from fifteen servers (five production deployments and ten public servers from the official MCP registry) with inter-rater reliability of Cohen's kappa 0.76. The paper reports tool-selection accuracy dropping below 90 percent between 10 and 15 tools per context for Claude Haiku 4.5.
Why it matters: It gives teams building MCP integrations a shared vocabulary and an empirical tool-count threshold to design around, relevant to the agentic-coding tooling this digest tracks.
Follow-up: Watch for the released replication package and independent validation of the tool-count finding on other models.