Ask your AI client to create a custom dimension, custom metric or formula metric in your Funnel workspace, or to update one you already have. Funnel MCP shows you a preview first and saves only the fields you choose. This works in any client connected to Funnel MCP, such as Claude, ChatGPT, Claude Code or Cursor.
Supported field changes
Through Funnel MCP, you can:
Create custom dimensions, custom metrics and formula metrics.
Update existing custom fields.
Preview fields with sample values before anything is saved.
Save all the fields in a preview, or only the ones you choose.
Through Funnel MCP, you can't:
Delete custom fields.
Create and update fields in the same preview. One preview covers 1 to 5 fields, and they're either all new fields or all updates.
To learn how custom dimensions work in Funnel, see Custom dimensions explained - The Basics.
To create a metric manually in Funnel instead, see Create a custom metric.
Before you begin
You have an AI client connected to Funnel MCP. To connect one, see Quick start guide: Using Funnel MCP.
You have the Edit fields permission in the workspace. You need it even to prepare a preview. If you don't have it, ask a subscription owner for Editor access. For more about roles, see Workspace: User roles.
Create or update custom fields
In your AI client, describe the field you want in plain language. For example:
Create a custom dimension called Channel group that puts Facebook and Instagram under Social.orCreate a formula metric for cost per conversion.
The client looks up the fields in your workspace and reads Funnel's guide to the rules for custom fields. It then prepares a plan for the new or changed fields.
Review the preview the client shows you. It lists each field Funnel MCP plans to create or update, with sample values. Nothing is saved yet.
Note: The preview expires after 1 hour. If it expires, ask the client to prepare it again.
Tell the client which fields from the preview to save. You can save all of them or only some.
If your client asks for its own approval to run the tool, approve it.
Note: If a field changed in Funnel after the preview, Funnel reports it as out of date and doesn't save it. Ask the client for a new preview of that field.
Custom field tools available in Funnel MCP
Your AI client selects these tools for you. You don't need to name them in your request.
Tool | Type | Description |
| Read | Finds dimensions, measures and metrics in the loaded workspace. |
| Read | Returns Funnel's guide to the rules for custom fields. |
| Write (preview) | Prepares a plan to create or update custom fields and shows you a preview. It doesn't save anything. |
| Write | Saves the fields you choose from the preview. |
What to expect
The fields you chose to save appear with the other custom dimensions and metrics in your workspace. Fields you didn't choose, and fields that Funnel reported as out of date, aren't saved.