Give your agent tools

Tools are extra powers, like running a command or calling a website. Here is how to add them.

On its own, an agent can only think and talk. Tools give it powers: reading a file, running a command, or calling a website. This guide shows the built-in tools and how to make your own.

Built-in tools

Some tools come ready to use. Just list them under tools:

agent writer
  model: anthropic/claude-sonnet-5
  tools:
    - fs_read
    - fs_write
  instructions: |
    Read notes.md, improve it, and save it back.

Tool	What it does
`fs_read`	Read a file.
`fs_write`	Write a file.
`fs_list`	List the files in a folder.
`bash`	Run a command in the terminal.

These all work inside the agent's sandbox, which keeps them safe.

Make your own tool

You can add your own tools with a tool block. There are two kinds: one that runs a command, and one that calls a website.

A command tool

Use type: shell to run a command. This one returns the current year:

tools.nt

tool current_year
  description: Returns the current four-digit year.
  type: shell
  command: date +%Y

Then let an agent use it by name:

agent age
  tools:
    - current_year

A website tool

Use type: http to call a web address:

tool lookup
  description: Looks up a record by its id.
  type: http
  url: https://api.example.com/records/{id}

Filling in the blanks

The {id} and {term} parts in curly braces are placeholders. The agent fills them in when it uses the tool. For example:

tool search_notes
  description: Searches the notes file for a word.
  type: shell
  command: grep -n "{term}" notes.md

When the agent runs this tool with the word "iPhone", NT replaces {term} with iPhone before running the command.

What a tool needs

Setting	What it does
`description`	Tells the agent when to use the tool. Write it clearly.
`type`	`shell` to run a command, or `http` to call a website.
`command`	The command to run (for `shell` tools).
`url`	The web address to call (for `http` tools).

The description matters

The agent decides when to use a tool by reading its description. A clear description like "Returns the current year" helps it pick the right tool at the right time.

Set up a sandbox

Control where tools can read and write.

Add a skill

Give your agent a reusable checklist.