Official (Anthropic)Active· 12d★ 4.3by Anthropic

Everything (reference)

Anthropic's reference MCP that exercises every protocol feature. Required reading if you're building your own MCP.

View repo

A+

Safety & Trust

Delv Safety Grade: A+

Score 94/100 · assessed 2026-04-18

Maintainer100

Permissions95

Supply chain95

Transparency90

Incidents100

This is Anthropic's official reference implementation for the MCP protocol, designed explicitly for developers building their own servers. It's maintained by the protocol authors themselves in the canonical servers repository. The server exercises every protocol feature through deliberately artificial examples (counters, echo tools, test prompts) rather than real-world functionality, which makes it safe by design. Distribution via npm with the @modelcontextprotocol scope provides strong supply chain guarantees. The permissions are minimal because it's a testing harness, not a production tool. It implements sampling and logging features, but these are protocol demonstrations rather than risky operations. Transparency is excellent with full source code in the main MCP repository. The only minor consideration is that it's a reference implementation meant for study, not production use, so developers might cargo-cult patterns without understanding their security implications in real contexts.

Green flags

Official Anthropic implementation, maintained by protocol authors
Artificial test features pose no real-world risk
Published via official @modelcontextprotocol npm scope
Full source code in canonical MCP servers repository
Designed explicitly as educational reference, not production tool

Red flags

Reference implementation may be cargo-culted into production without adaptation
Sampling feature demonstrates external LLM calls that could be misunderstood

Permissions requested

Outbound networkExternal LLM call

Assessed by Delv Editorial using public metadata. Grades are advisory and update as the ecosystem changes. They do not replace your own review of permissions and code before granting an agent access to sensitive systems.

Install

npx -y @modelcontextprotocol/server-everything

Review

Everything is Anthropic's reference implementation that exercises every single MCP protocol feature. It's not a production tool. It's a Rosetta Stone. If you're building your own MCP server, this is the codebase you clone and study. It implements resources, tools, prompts, sampling, logging, and every edge case in the spec. I've used it to verify my own server implementations, and it's saved me hours of head-scratching over protocol details that aren't obvious from the docs alone. The server exposes a deliberately artificial set of features: a counter resource, an echo tool, a prompt that generates boilerplate. None of these do anything useful in isolation. The point is to show you how each protocol primitive works in context. When I was debugging why my custom server's resource subscriptions weren't firing, I traced through Everything's implementation and found I'd missed a notification callback. That's the workflow: run Everything alongside your own server, compare behaviour, fix your code. It's also useful for testing MCP hosts. If you're building a client that consumes MCP servers, Everything will exercise every code path. You'll know immediately if your host chokes on sampling requests or can't handle dynamic resource updates. The code is clean, well-commented TypeScript. You can read it in an afternoon. Who shouldn't bother: anyone looking for a tool to actually use. This is scaffolding, not a building. If you're just consuming MCP servers in Claude Desktop, you'll never need this. It's for implementers only. The features it exposes are intentionally trivial because the point is the protocol, not the functionality. I'd also skip it if you're not comfortable reading TypeScript. The value is in the source, not the runtime behaviour.

Verdict

Essential reference material if you're building MCP servers or clients. Useless otherwise. Install it, read the code, compare it to your implementation. Don't expect it to do anything productive on its own.

Good at

Implements every MCP protocol feature in one place, so you can see how they interact.
Clean, readable TypeScript that's easier to follow than the spec docs alone.
Catches edge cases you'd miss if you only read the protocol documentation.
Useful for testing whether your MCP host implementation handles all primitives correctly.

Watch out

Zero practical utility outside of development and testing contexts.
The exposed features are intentionally trivial, which can be confusing if you expect real functionality.
No documentation beyond the code itself, so you need to be comfortable reading TypeScript.
Overkill if you only need to understand one or two protocol features rather than the entire spec.

Getting started

1. Run `npx -y @modelcontextprotocol/server-everything` to install and start the server. 2. Add it to your Claude Desktop config under `mcpServers` with the command from step 1. Restart Claude. 3. In Claude, check the MCP icon to verify the server appears. You should see resources like 'counter' and tools like 'echo'. 4. Try the echo tool with any text. It should return your input unchanged. This confirms the protocol is working. 5. Watch out: the features are deliberately trivial. Don't expect useful output. The value is in comparing the source code to your own server implementation.

Works with

Claude DesktopClaude Code