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

# Using Tools in Prompts

Registry tools can be added to any prompt in the Playground. Instead of defining tool schemas inline, you reference them from the registry — keeping prompts clean and tool definitions centralized.

## Adding a Registry Tool

1. Open a prompt in the **Playground**
2. Click **+ Add Tool** → **From Registry**
3. Browse or search for the tool you want
4. Select a **version** or **release label** (e.g., "production")
5. The tool is added as a reference

The tool appears in your functions list with the tool name and label badge (if you selected one).

<Frame>
  <img src="https://mintcdn.com/promptlayer/et_v3mDNh4k4_HuA/images/tool-registry/registry-tool-reference.png?fit=max&auto=format&n=et_v3mDNh4k4_HuA&q=85&s=1b5af3392b482c7cb47dbe3d0f31d0e9" alt="Registry tool reference in prompt" width="1864" height="988" data-path="images/tool-registry/registry-tool-reference.png" />
</Frame>

<Tip>
  The LLM never sees registry references. At render time, they're transparently replaced with the resolved function definitions.
</Tip>

## What Gets Stored

Your prompt template doesn't store the full tool definition. It stores a lightweight reference:

```json theme={null}
{
  "type": "registry",
  "tool_registry_id": 5,
  "label": "production"
}
```

When the prompt is fetched via the API, this reference is replaced with the actual function definition. This means:

* Updating the tool in the registry updates **all prompts** using it
* Moving a label to a new version takes effect **immediately**
* No prompt edits or redeployments needed

## Running in the Playground

Registry tools work seamlessly in the Playground. When you click **Run**, the tool definitions are resolved from the registry and sent to the LLM. The LLM sees standard function definitions — it has no concept of the registry.

## Deleting a Tool

When you delete a tool from the registry:

* A warning dialog shows all affected prompts
* The tool reference is removed from all prompt templates
* The tool is soft-deleted

<Warning>
  Deleting a tool removes it from all prompts that reference it. Check the References tab first to understand the impact.
</Warning>

## API

See the [API Reference](/reference/tool-registry-list) for the full list of endpoints, or check the [Overview](/features/tool-registry/overview) page for common curl examples.