The MCP Engineering Handbook — Companion Samples

Code samples for the book, written against the 2026-07-28 MCP specification using the v2 GA SDKs. Every project was rebuilt and smoke-tested on the GA releases (2026-08-19); the TypeScript projects were re-run on 2.2.0 (2026-10-12).

SDK pins

Versions are pinned exactly. C# and Python are on the 2.0.0 GA. TypeScript moved to 2.2.0: @modelcontextprotocol/client 2.0.0–2.1.x is affected by GHSA-6qxp-vccf-f47h (the OAuth client could send credentials to an authorization server the MCP server names). No sample uses the OAuth client, but samples get copied; the server package moved with the client so the two stay in lockstep.

Language	Package	Version
C#	ModelContextProtocol (+ .AspNetCore where used; .Extensions.Tasks for the tasks extension)	2.0.0
Python	mcp	2.0.0
TypeScript	@modelcontextprotocol/server, @modelcontextprotocol/client (@modelcontextprotocol/node 2.1.0 for the Node HTTP adapter in chapter01/http-server)	2.2.0

Do not use the v1 TypeScript monolith (@modelcontextprotocol/sdk) — v2 ships as the two packages above. One sample temporarily pins a dependency to git rather than PyPI: chapter12/agent-as-mcp uses a Microsoft Agent Framework commit with mcp 2.x support until a release ships it — see its README. (It and chapter07/health-dashboard used to ride the v1 mcp line until their ecosystems adopted v2.)

Layout

chapterNN/<sample-name>/
  csharp/      dotnet 10; dotnet run
  python/      uv; uv run python server.py
  typescript/  Node 20+, ESM; npm ci && npm run build && npm start
  README.md    what it demonstrates + chapter section reference
templates/hello-server/   walking skeleton in all three languages (toolchain check)

Samples

Sample	Book ref	Languages
chapter01/stdio-server/	§1.7	C# (canonical), Python, TS
chapter01/http-server/	§1.7–1.8	C# (canonical), Python, TS
chapter01/client/	§1.8	C# only (by design; Ollama-wired, LLM API alternatives included)
chapter02/long-running-operation/	§2.6.4	C# (canonical), Python, TS
chapter03/demo-resource-server/	shared by ch3 samples	C# (canonical), Python, TS
chapter03/resource-client-host/	§3.3.1	C# (canonical), Python, TS
chapter03/model-resource-client/	§3.3.3	C# (canonical), Python, TS
chapter03/resource-link-client/	§3.3.4	C# (canonical), Python, TS
chapter05/progressive-disclosure/	§5.1.2	TS (canonical), C#, Python
chapter05/preview-before-execute/	§5.1.4	C# (canonical), Python, TS
chapter05/completions/	§5.3.3	Python (canonical), TS, C#
chapter05/low-level-handlers/	§5.4.1/§5.4.3	TS + Python (canonical), C#
chapter05/csharp-filters/	§5.4.2	C# only (by design)
chapter05/mcpb-bundle/	§5.5.1/§5.5.2	Node (bundle fixture)
chapter06/schema-mapping/	§6.2.2/§6.2.3	TS (canonical), C#, Python
chapter06/mrtr-client/	§6.2.5	TS (canonical), C#, Python
chapter06/task-injection/	§6.2.11	C# (canonical), Python, TS
chapter07/health-dashboard/	§7.4	TS only (Apps SDK; ext-apps 2.0.3)
chapter07/tasks-polling/	§7.3	C# (client-side task methods, minimal)
chapter09/token-validation/	§9.2.2/§9.2.4/§9.2.7	C# (canonical)
chapter09/stepup-client/	§9.7.4	C# (union rule + naive anti-pattern)
chapter10/eval-harness/	§10.1	C# (canonical) + minimal TS
chapter10/otel-wiring/	§10.2	C# only (by design)
chapter10/mcp-proxy/	§10.4.3/§10.5	C# (canonical)
chapter12/channel-pattern/	§12.4 (+§12.2 harness miniature)	C# (canonical; server + chat surface + harness)
chapter12/agent-as-mcp/	§12.3	Python only (MAF as_mcp_server(); MAF pinned to a git commit for mcp 2.x — see its README)
templates/hello-server, templates/hello-client	—	toolchain skeletons

SDK behavior notes (verified at GA, 2026-08-19)

• All three SDKs serve handshake-less 2026-07-28 requests over stdio, and all three validate the _meta envelope strictly: modern-era requests need clientInfo, clientCapabilities, and protocolVersion, or the request fails with -32602. (The preview-era C# leniency is gone at GA.) tools/list responses carry ttlMs/cacheScope from all three SDKs.
• TypeScript stdio servers must use serveStdio(factory) — hand-wiring server.connect(new StdioServerTransport()) serves no server/discover (-32601), so negotiating clients fall back to the legacy era (2025-11-25).
• TypeScript clients default to the legacy negotiation posture — pass versionNegotiation: { mode: 'auto' }. This did not change at GA.
• Python stdio serves both eras, locked per connection by the opening message: the high-level MCPServer.run() stdio path answers server/discover and accepts handshake-less 2026-07-28 requests (as does the low-level Server path and streamable HTTP); a connection opened with initialize instead negotiates 2025-11-25 and then rejects modern-envelope requests with -32600. The Python client's mode='auto' negotiates 2026-07-28 against these servers and falls back to initialize against old ones.
• Version-negotiation defaults differ per SDK: Python client auto-probes the modern era by default, TypeScript defaults to legacy (pass versionNegotiation: { mode: 'auto' }), C# negotiates modern with no option needed.
• C# tasks extension is a separate package at GA: ModelContextProtocol.Extensions.Tasks (.WithTasks(store), CallToolAsTaskAsync, CallToolWithPollingAsync) — see chapter07/tasks-polling/.
• Toolchain prerequisites: .NET 10 SDK, Node.js ≥ 20, uv (Python projects pin their own interpreter, ≥ 3.12).