Tool-calling agent

Runs locally

Needs Ollama with qwen3:14b pulled, or any other model that takes tools. No key. The weather tool calls the public wttr.in service.

In Boltjar a tool is a small branch of nodes. The model sees a name and a description; when it calls the tool, the branch runs with the model’s arguments, and whatever reaches the end of the branch goes back to the model. This graph gives a local model two tools: the time on your computer, and the weather in a city.

Download the graph and save it in user/graphs/, or build it below. The graph is MIT-0: copy it and license what you build from it however you like.

1. The chat

The same chat as in Chat with Ollama: a Chat Input named Message, a Prompt, an LLM and a Chat node, wired the same way. The downloaded graph has no model picked: pick one that takes tools on the LLM, such as Qwen3 14B (Ollama). Its tool sockets, and the wires from the two Tool nodes into them, show once that model is picked. Use this Prompt:

You are a helpful assistant. Use your tools when they help.

User: {message}

2. A tool without arguments: get_time

Node	Settings
Tool, named get_time	name get_time, description Returns the current date and time on this computer.
Tool Args, named get_time args	fields empty
Time, named Now	format Monday 08 Jun, 02:30 PM
Template, named Time answer	It is {now}.

From	To
get_time call	LLM + tool (it becomes tool0)
get_time call	get_time args call
get_time args trigger	Time answer trigger
Now out	Time answer now
Time answer out	get_time result

Right-clicking a Tool offers to add its Tool Args already wired. Wiring the Template’s trigger makes it assemble when the tool is called and send the text on, and that text landing on result is the tool’s answer. The {now} tag is named after the Now node, the way a dropped wire names a tag.

3. A tool with an argument: get_weather

Node	Settings
Tool, named get_weather	name get_weather, description Returns the current weather for a city, in one line.
Tool Args, named City	fields city
HTTP Request, named Weather API	method GET, url https://wttr.in/{city}?format=3, response text

From	To
get_weather call	LLM + tool (it becomes tool1)
get_weather call	City call
City trigger	Weather API trigger
City city	Weather API + tag (it becomes city)
Weather API body	get_weather result

Typing city in the Tool Args fields does two things: the node grows a city output, and the tool tells the model it takes a city argument. The Tool’s schema mode stays auto for that. A wire dropped on the HTTP Request’s + tag makes a tag named after the node it comes from, which is why this Tool Args is named City: its wire becomes the {city} in the url.

4. Ask

Press On and ask “What time is it?” or “How is the weather in Lisbon?”. The model decides whether to call a tool; each call runs its branch, and the Tool node shows the arguments and the result. A reply can take up to six rounds of tool calls before the model has to answer.

How it works

• The model only sees the Tool’s name and description, and the parameters. Write the description for the model: say what the tool returns and when to use it.
• Tool calls work with Ollama, xAI, Anthropic, OpenAI and OpenAI-compatible models that take tools, as their manifest or their provider says. The LLM page lists the ones that ship with a manifest.
• Two tools cannot share a name, and a tool needs one: the graph will not turn On otherwise.
• If a branch never sends a result, the model gets an error for that call after two minutes.
• A tool branch is a graph like any other: DB lookups, Read File, HTTP Request with a {{secret.NAME}} key. Keep in mind that the model chooses the arguments, so treat them as untrusted input (Security).