Copilot Studio Variables Guide: Global vs Topic Scope & Passing Values (Avoid Choice Type Errors)

• String: Text
• Bool: true or false
• Number: Numeric values
• Table: Tables (including arrays)
• Record: Records (objects)
• DateTime: Date and time
• Choice: Options (⚠️ behaves differently from Power Apps)
• Blank: Blank (same as blank in Power Apps)

Among these, the “Choice” type differs significantly from Power Apps. In Power Apps, table-type values are often used as options for controls like combo boxes. However, in Copilot Studio, “Choice” is treated as a distinct strict type. You cannot simply pass a string into a Choice variable without conversion.

Additionally, entities themselves are not considered “types” but act as definitions for types. For example:

• “Age,” “Currency,” “Count”: Treated as Number type
• “Postal Code,” “Country,” “City”: Treated as String type
• “User-defined entities,” “Multi-select options”: Treated as Choice type

• Topic Variables: Accessible only within the current topic. (Local scope)
• Global Variables: Accessible across all topics in the agent.
• System Variables: Pre-defined variables managed by Copilot Studio (e.g., User ID, Last Message).
• Environment Variables: Defined at the Power Platform environment level (ALM-friendly).

To demonstrate the difference, I set up two topics: “Calling Topic” and “Called Topic.”

In the “Calling Topic,” I defined both a topic variable and a global variable:

When I switch to the “Called Topic” and try to access variables, only the global variable is visible.

※ Technically, global variables are accessible from ANY topic within the agent.

As expected, the message in the “Called Topic” successfully displays the value from the Global Variable defined in the “Calling Topic”.

According to the official documentation, global variables retain their value until:

• The session ends (conversation reset).
• The “Clear Variable Value” node is explicitly used.

You can use the “Clear Variable Value” node within the system topic “Reset Conversation” or anywhere in your logic to reset data.

In the destination topic, go to [Details] > [Inputs] and click “Create a new variable.” This defines an argument that the topic expects to receive.

Now, in the “Calling Topic,” when you add a Redirect node, you will see an option to [Add an input].

Select the variable you want to pass (in this case, a local topic variable).

Result: The value is successfully passed without polluting the global scope.

To return data back to the original topic, go to [Details] > [Outputs] and create a new variable.

Inside the topic, assign the final result to this output variable using the [Set a Variable] node.

The “Calling Topic” can now access this return value immediately after the redirect node finishes.

These are built-in variables useful for logic conditions:

• Activity.Text: The latest user input text.
• LastMessage.Text: The previous message sent by the user.
• User.Email: The authenticated user’s email.
• User.PrincipalName: The user’s UPN.

※ Tip: Activity.Text is for the current turn, while LastMessage.Text is historical.

Define them in your Solution:

Use them in topics (e.g., switching SharePoint URLs dynamically):

Important: When exporting your solution, ensure the environment variables are included as required objects.