Benchmarks Show Stdio Is 9x Faster Than SSE for MCP Tool Calls

A benchmark of 10,000 tool executions compared the two main Model Context Protocol transports — Stdio and Server-Sent Events (SSE) — to assess their impact on AI agent performance. Stdio delivered a mean latency of 2.1ms versus 19.4ms for remote SSE, with SSE also adding up to 45ms for connection setup due to TCP handshakes and TLS. The gap becomes significant in autonomous agents like Cursor or Claude Desktop, where 10–15 sequential tool calls are common and overhead compounds quickly. Stdio is recommended for local developer and desktop environments, while SSE remains better suited for multi-tenant cloud setups requiring authentication and rate-limiting controls. Memory usage also varied, with compiled Go or Rust workers consuming under 7MB per process compared to around 42MB for a centralized SSE daemon.