---
title: "set_variable_value"
description: "Set ONE variant's value on a grouped variable, preserving every other variant."
sidebarTitle: "set_variable_value"
lastUpdated: "2026-09-23"
---

> **For AI agents:** the complete documentation index is at [llms.txt](/llms.txt). Append `.md` to any page URL for its markdown version.

{/* GENERATED FILE: do not edit by hand. Regenerate with: node scripts/generate.mjs */}

Set ONE variant's value on a grouped variable, preserving every other variant.

<Info>
  **Writes data · Idempotent · Calls external systems.**
</Info>

## Parameters

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `acknowledge` | boolean | No | Reset edit budget after user approval |
| `value` | string | Yes | New value for this variant |
| `variable_id` | number | Yes | Variable id (must be group-scoped) |
| `variant` | string | Yes | Variant id (number) or name (string) |

## Example arguments

Illustrative arguments an agent supplies when calling this tool:

```json
{
  "variable_id": 0,
  "variant": "string",
  "value": "string"
}
```

## Description

```text
variant accepts the variant id (number) or name (string); name resolution loads the parent group's variants. Errors when called on a global variable — globals have no variants; use update_variable default_value instead. Errors when the variant is not present on the variable.

This sets ONE variable in ONE variant. To bulk-copy ALL variables' values from one variant into another across the whole group, use copy_variant_values instead.
```

## Related

- [`update_variable`](/mcp/tools/variables/update_variable)
- [`copy_variant_values`](/mcp/tools/variables/copy_variant_values)

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