> For the complete documentation index, see [llms.txt](https://docs.intentable.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.intentable.io/intent-structure/variables/external.md).

# External

External variables are provided to the FCT Engine as an array of bytes32 values by the activator. This values might contain any native type, e.g. uint256, bytes32, address, bool, etc.

#### Usage

*0xFC000....0000LLLL*\
\&#xNAN;*LLLL* holds the variable index inside the provided variable array (starting with 1)<br>

**External variable use four  range of values:**\
\
`For address types:`\
\&#xNAN;*`0xFC00000000000000000000000000000000000001`*\
`...`\
\&#xNAN;*`0xFC0000000000000000000000000000000000ffff`*\
\
`For uint256 and bytes32 types:`\
\&#xNAN;*`0xFC00000000000000000000000000000000000000000000000000000000000001`*\
`...`\
\&#xNAN;*`0xFC0000000000000000000000000000000000000000000000000000000000ffff`*<br>

{% hint style="success" %}
`FC stands for "Future Changeable"`
{% endhint %}

{% hint style="warning" %}
The activator sets values for variables when executing the FCT. Be careful when using external variables.
{% endhint %}

{% hint style="success" %}
A common use case is to build p2p swap FCT with two calls. The first one, for example, sending X tokens a variables address (0xFC...0001) and the second one is getting Y ether from that address (0xFC.....0001)
{% endhint %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.intentable.io/intent-structure/variables/external.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.