The tools we actually run.

Open-source and source-available MCP servers, agent skills and developer tools R21 uses in production — each one credited, licence-checked and dated. Where something replaces a product you would otherwise pay for, we say so and link the price.

MCP servers

3

Servers that connect an assistant to a real system — a database, an EHR, a docs index — without handing it credentials.

Agent skills

2

Instruction libraries that change how a coding agent works, rather than what it can reach.

Developer tools

4

Things R21 runs alongside the agents: browsers, code understanding, verification.

Built by R21

3

Software R21 designed and shipped. Listed for what it demonstrates, not as something you install.

Playbooks

2

How R21 wires and runs the things above, written from the real thing rather than assembled from a tool list. Long-form.

Something missing?

If you run something that belongs here — especially if it does a job people currently pay for — send it over. Every suggestion is read by a person, and most are not published.

Suggest a tool