> ## Documentation Index
> Fetch the complete documentation index at: https://arize-ax.mintlify.site/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Test tool calls

> Debug tool calls directly in prompt playground

Prompt Objects in Arize AX store the tools/functions that your LLM calls have in context, letting you experiment with different tools and tool signatures.

<Frame>
  <video
    src="https://storage.googleapis.com/arize-phoenix-assets/assets/images/tools.mp4"
    width="100%"
    height="100%"
    style={{
  display: 'block',
  objectFit: 'fill',
  backgroundColor: 'transparent'
}}
    controls
    autoPlay
    muted
    loop
  />
</Frame>

Tools are a key part of agentic workflows, but debugging tool use can be tricky:

* Were there any unclear parts in the function description or parameter details?
* Was the function used with the right parameter values?
* If the correct function existed, did the LLM use it?
* Did the LLM have the needed function to reply to the input?

The playground automatically pulls in tools from your span data, making it easy to iterate on tool call prompts, especially if you have [traced your function calls](/docs/ax/instrument/what-are-traces).

Configure/add tools when you click the **Functions** button.

* Functions are calibrated as JSON objects. To add multiple functions, simply populate the list with more JSON objects.
* Configure your **Functions Selection**. This gives the LLM extra instructions on how/when to decide a function from the list should be invoked.