Module 3 · Running servers in production · Lesson 8

Shipping and evolving servers

Treat tool names, schemas, annotations and descriptions as a public contract, check every change against it in CI for both protocol eras, fit the limits of the hosts your server runs in, and ship it with structured logs, an npm package and a registry entry.

85 min 1 video 3 exercises 8-question quiz Answers

Setup for the exercises:Install Claude Code Node.js, pnpm and TypeScript Run evals in GitHub Actions The Larchmere Desk mock API

By the end of this lesson you can

Classify a change to a tool's name, schema, annotations or description as breaking, compatible or needing review, and deprecate instead of breaking
Build a contract check that snapshots tools/list and fails CI on an unannounced breaking change, alongside Inspector CLI checks for both protocol eras
Fit results, descriptions and server instructions to host limits on output size, description length and timeouts, including tool search
Write structured logs to stderr that carry the caller's W3C trace context from request metadata
Package a server for npm and the MCP Registry, and check it against a host's connector review criteria

The designed larchmere-desk server has been live for three weeks. A pull request tidies it up: open_incident becomes declare_incident, search_help_articles returns at most 3 articles instead of 5, get_ticket_context drops suggested_articles, and update_ticket is relabelled as non-destructive. Each change looks harmless in review. Then the triage agent, which reads suggested_articles in code, crashes; a colleague's Claude Code allow rule for mcp__larchmere-desk__open_incident silently stops matching; and in Claude, which uses annotations for auto-permissions, update_ticket no longer counts as a destructive tool that always prompts. A REST API breaks its consumers in the same ways, but its consumers read changelogs and pin versions. An MCP server's main consumer reads the tool list fresh at the start of every session and has never seen a changelog. This lesson is about shipping a server whose changes don't surprise anyone.

Shipping and evolving servers

Shipping and evolving servers

Shipping and evolving servers

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