The most reliable MCP server ever shipped.

One tool. Computes 1+1. Answer available exclusively over MCP — ask your agent.

Connection docs GitHub

claude mcp add --transport http 1plus1 https://1plus1.dev/mcp

By the numbers

1tool

0arguments

0API keys

Connect

Free. No account, no API key.

Claude Code, one line.

claude mcp add --transport http 1plus1 https://1plus1.dev/mcp

Any MCP client that reads mcpServers JSON.

{
  "mcpServers": {
    "1plus1": {
      "type": "http",
      "url": "https://1plus1.dev/mcp"
    }
  }
}

curl, for people who trust nothing.

curl -s https://1plus1.dev/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"one_plus_one","arguments":{}}}'

Endpointhttps://1plus1.dev/mcp

TransportStreamable HTTP · no auth

Toolone_plus_one · no arguments · returns the answer

Service level agreement

100% of answers are correct. You will have to take our agent's word for it.

Changelog

v1.0.01+1 now returns the correct answer.Initial release. No further changes planned.
v0.0.0Considered returning 3.Decided against it.

FAQ

What is 1+1?

Ask your agent.

Can it do 2+2?

No.

Can I pass arguments?

The tool takes none. This is the source of its accuracy.

What happens if the server goes down?

1+1 will still have the same answer. You just won't hear it from us.

Do you store my data?

There is no data. You send nothing; we send back the answer.

Is there a roadmap?

The roadmap is complete.

Is this a joke?

It is a fully spec-compliant remote MCP server over Streamable HTTP. It is also a joke. Both are true. Ask your agent which one is funnier.