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Claude Code MCP Shows Connected but 0 Tools: "Invalid result for tools/list" (ttlMs / cacheScope), Reproduced and Fixed
An MCP server shows as connected but exposes 0 tools, and the log says Invalid result for tools/list with ttlMs and cacheScope failing validation. Reproduced with a stub server on Claude Code 2.1.280, 2.1.285 and 2.1.288: the cause is not extra fields being rejected. The server negotiated MCP 2026-07-28 and then left out fields that revision requires (resultType, ttlMs, cacheScope); adding unknown fields works fine. Whether stdio uses the new protocol is decided by a remote flag that is off by default, so the same version breaks for some users and not others, and 2.1.280 fails the same way once negotiation is on. MCP_PROTOCOL_NEGOTIATION=legacy (also works in settings.json env) restores the tools; servers fix it by adding the three fields.
mcpclaude-code+4
pitfallsOct 3, 20268 min
192
Claude Code MCP server Failed to connect: CONNECTION_CLOSED, connection timed out after 30000ms and ENOENT, reproduced one by one
Six causes behind Claude Code's MCP "Failed to connect", reproduced on 2.1.280: mcp list exits 0 on failure, CONNECTION_CLOSED hides two causes that only --debug-file reveals, and one server that never handshakes pushes claude -p wall time 4.63s → 36.21s, duration_ms only 4323.5 → 5930.
mcpclaude-code+4
pitfallsSep 24, 202610 min
337The New MCP Roadmap: Five Priorities, One HTTP Transport to Rule Them All (0822)
The Model Context Protocol team published a new roadmap with five priority areas: agentic messaging primitives, HTTP-native transport unification, agent identity, improved primitives, and SDK ergonomics. Here's what each one means for your MCP integrations.
aillm+3
developerAug 23, 20265 min
325July 28 Was MCP's Coming of Age: The Protocol Dropped State, the Ecosystem Got Its First Lawsuit
Two milestones in one day. The largest MCP spec revision ever shipped: the initialize handshake and session IDs are gone, the core goes stateless, and Roots, Sampling, Logging, and HTTP+SSE enter a 12-month deprecation countdown. The same day, gateway startup Runlayer sued Rippling, alleging a year-long 'customer trial' that ended in a cloned product — MCP's first commercial lawsuit. What breaks, what each kind of developer should do, and why these two events read as one story.
llmmcp+7
ai-tutorialsJul 29, 20268 min
432Claude Code MCP: Connect External Tools and Data Sources
Learn how Model Context Protocol (MCP) lets Claude Code connect to databases, APIs, and third-party services to extend your AI coding assistant's capabilities.
mcpclaude-code+2
claudeApr 13, 20262 min
707Claude MCP Guide: Connect Claude to Tools and Data the Reusable Way
How to use the Model Context Protocol with Claude to connect tools, databases, and services in a reusable and standardized way.
claudemcp+2
ai-tutorialsMar 29, 20263 min
200Claude Certified Architect – Foundations: The Official Exam Guide Explained
A comprehensive breakdown of Anthropic's Claude Certified Architect – Foundations certification exam guide, covering all 5 domains, 6 exam scenarios, sample questions with explanations, preparation exercises, and key technologies.
prompt-engineeringclaude+4
ai-tutorialsMar 18, 202614 min
3604