MCP servers
A server’s tools are available from the next turn, named
mcp__<server>__<tool>. In a server’s settings, ${NAME} is replaced with the
secret called NAME. nu mcp remove removes a server.
Hosted servers that use OAuth, such as Linear’s and Notion’s, need a sign-in:
Open the link it prints and sign in. The client catches the redirect and saves
the sign-in as the secret MCP_LINEAR. If a server won’t register Nu as a
client, create an OAuth app with the callback http://127.0.0.1:4123/callback
and pass its --client-id and --client-secret.
Servers are kept in ~/.nu/mcp.json, in the same mcpServers format other
clients use:
Servers started with a command run inside the Nu container with Nu’s own
access. Only add ones you trust.
~/.nu/workspace/tools/ and opens it when it needs to look.
Packages
Packages add tools, skills, and chat apps. nu search finds packages on npm,
and Nu can search for one when you ask. Install one from npm or Git, or ask Nu
to install it:
nu install ./my-package installs a folder on your machine, such as a package
you are writing, by sending its files to Nu. Run it again after a change. A
changed tool needs a higher version in its tool.yaml. Nu lists the package
as local:<namespace>, and nu remove ./my-package removes it.
Installing a package again updates it. A tool whose code changed without a
higher version, or whose version went down, stops the install, and the
installed package stays as it was.
Before installing, Nu shows what each tool does and which secrets it needs.
When Nu installs a package itself, the approval names the exact npm version or
Git commit, and that is what gets installed. Package tools run in their own
process. They can’t read files and see only the secrets they list.
Skills
A skill is a folder in ~/.nu/skills with a SKILL.md that tells Nu how to do
something. Nu reads a skill when a task calls for it, and can write new ones
when you ask. Packages can include skills too.
Specialists
A specialist is an agent with its own instructions, tools, rules, and memory.
Ask Nu to make one, such as “make a researcher that searches the web, on a
smaller model”. You approve it before it’s saved to
~/.nu/specialists/<name>.yaml:
tools can name MCP tools too. mcp__<server>__* gives a specialist all of a
server’s tools, including ones the server adds later.
Nu hands specialists tasks on its own. To talk to one directly, use
/specialist <name>. A specialist without a model uses Nu’s, and so does one
whose model isn’t available.
Secrets
Tools, MCP servers, and packages share one set of secrets, stored in
~/.nu/secrets/secrets.json:
/secret NAME value in chat does the same. The agent itself never sees a
secret. Each tool gets only the ones it asks for, when it runs.
Nu