The parts of building an MCP server that the tutorials skip

Short summary

A practical guide to the unglamorous problems that kill production MCP servers: stdout collisions on stdio transport, untyped errors that cause agents to retry doomed calls, SSRF vulnerabilities in fetch tools, and silent OAuth failures. An April 2026 scan found 52% of 2,181 remote MCP endpoints dead and only 9% healthy. The author provides concrete code patterns for each issue and references a MIT-licensed starter kit.

• •52% of 2,181 remote MCP endpoints are dead; only 9% are fully healthy — failures come from infrastructure around the protocol, not the protocol itself
• •Key pitfalls: stdout collisions, untyped errors causing agent retry loops, SSRF via fetch tools, and silent OAuth failures
• •Provides typed error classes, SSRF host allowlists, and bearer-token auth patterns with code examples

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