> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/cortex-xdr-5.x/detect-investigate-and-respond-to-threats/threat-management/detection-rules/whats-a-correlation-rule/field-replacement-syntax-in-correlation-rules.md).
# Field replacement syntax in correlation rules
When creating correlation rules, it's possible to use predefined values for different fields in the editor, such as **Alert Name**, **Alert Description**, and **Drill-Down Query**. These predefined values follow a certain syntax and are dependent on the Cortex Query Language (XQL) query for the correlation rule that you build in the **XQL Search** and **Drill-Down Query** areas in the editor. For example, if you define the **Alert Name** to be something, such as `Alerts based on $agent_name`, the XQL query defining the correlation rule must have the `agent_name` field defined in the logic of the query; otherwise, this field won't be replaced.
Standard field replacement
Syntax
```
$
```
The following text is added to the **Alert Description** field in the correlation rule editor, which uses a regular field:
`The user's registered email is: $Email`
Example Results:
If the `Email` field is a saved value containing `john.doe@example.com`, the output of the Alert Description is:
`The user's registered email is: john.doe@example.com`
The following text is added to the **Alert Description** field in the correlation rule editor, using an XDM field:
`The user's registered email is: $xdm.email.recipient`
Example Results:
If the `xdm.email.recipient` field is a saved value containing `john.doe@example.com`, the output is:
`The user's registered email is: john.doe@example.com`
Keep in mind the following:
* `` identifiers must consist exclusively of alphanumeric characters (a-z, A-Z, 0-9) and underscores (`_`).
* Cortex Data Model (XDM) fields can include dot (`.`) characters.
* While `` identifiers can begin with a numeric character, the fields cannot be composed solely of numeric characters. For example, `$123_data` is permissible, whereas `$456` is not.
* Text enclosed with double quotes (`""`) is treated as a literal string and will not undergo field replacement.
The following text is added to the **Alert Description** field in the correlation rule editor:
`The user's registered email is: "$Email"`
Example Results:
Since the syntax is invalid, it's ignored and the same text is displayed:
`The user's registered email is: "$Email"`
Fields with special characters
When field names contain characters that are not permitted in the standard `$` syntax, such as spaces, hyphens, or special symbols, the field name must be enclosed within backticks (` `` `)
Syntax
```
$``
```
The following text is added to the **Alert Description** field in the correlation rule editor, using a field containing characters that are not permitted:
`` Report Title: $`Annual Sales Report - Q1 2025` ``
Example Results:
If the Annual Sales Report - Q1 2025 field is a saved value containing `Executive Summary`, the output is:
`Report Title: Executive Summary`
---
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