--- title: "AI agent variables" slug: "ai-agent-variables" updated: 2026-09-30T11:47:25Z published: 2026-09-30T11:47:25Z canonical: "docs.voiso.com/ai-agent-variables" --- > ## Documentation Index > Fetch the complete documentation index at: https://docs.voiso.com/llms.txt > Use this file to discover all available pages before exploring further. # AI agent variables **Who should read this article**: Administrators Variables let an AI agent use details about the call and the lead it is calling. You insert a variable into the agent's **Greeting message** or **Prompt**, and on each Dialer campaign call, Voiso replaces it with the value for that call. For example, this greeting: `Hi {{context_first_name}}, this is Anna from Acme. I'm calling about your {{context_plan}} plan.` is spoken to the lead as: *"Hi Maria, this is Anna from Acme. I'm calling about your Premium plan."* Dialer campaign calls only Variables are filled in only on calls from a [Dialer campaign](/v1/docs/outbound-dialer-campaigns-overview). They are not filled in on inbound calls, or when you talk to the agent in the **Test** panel. If the agent also handles inbound calls, write the prompt so it still works when the values are missing. ## Types of variables Variables come in two groups. | Group | What it contains | Setup needed | | --- | --- | --- | | **System variables** | Details of the call itself: the date, the time, and the campaign name. | None. You can insert them in any Voiso agent. | | **Custom variables** | Fields from your Dialer campaign leads, such as a first name, company, or plan. | Map the field on the [Interaction context mapping](/v1/docs/interaction-context-mapping) page with **Voiso AI Agents** selected under **Show in**. | ### System variables | Variable | What it contains | Example | | --- | --- | --- | | `system_call_date` | The date of the call, with the day of the week, in your contact center's time zone. The date is written in English. | Friday, 21 August 2026 | | `system_call_time` | The time the call started, in your contact center's time zone, in 24-hour format. | 14:32 | | `system_campaign_name` | The name of the Dialer campaign the call belongs to. | Summer promo 2026 | Tip An AI agent has no clock of its own. Use `system_call_date` and `system_call_time` when the agent needs to know what day it is, say whether your office is open, or suggest a time for a callback. ### Custom variables Each field you map on the **Interaction context mapping** page can become a variable. Its name is the field's **Auto-generated context key**, which always starts with `context_`. For example, a field with the display label **Company name** becomes `context_company_name`. A custom variable is available to your AI agents when: - its **Metadata source** is **Dialer campaign lead list** (leads from a CSV upload or the Calling List API), and - **Voiso AI Agents** is selected under **Show in** for that field. On each call, the variable takes its value from the lead being called. Values longer than 256 characters are cut to 256. Note - Custom variables appear in the list only for users who can view the **Interaction context mapping** page. Other users see the system variables only. - Fields mapped before Voiso AI Agents could use them were switched on automatically, if their only source is **Dialer campaign lead list**. A field that also uses the **SIP header** source cannot be used by AI agents. Create a separate field for the dialer source instead. ## Inserting a variable 1. From the Voiso navigation bar, navigate to **AI Agents > AI Agents** and click the agent's name. 2. In the **Agent behavior** section, click in the **Greeting message** or **Prompt** field where you want the value to appear. 3. Type `{{`, or click the **Variables** icon (`{ }`) in the bottom-right corner of the field. The list of variables opens, grouped into **System variables** and **Custom variables**. Custom variables are listed by their **Display field label**, with the variable name next to it. 4. To narrow the list, keep typing. The search matches both the display label and the variable name. 5. Point at a variable to see its details: - For a system variable: an **Example** value. - For a custom variable: its **Display field label**, **Auto-generated context key**, and **Metadata source**. 6. Click the variable to insert it. It appears in the field in double braces, for example `{{context_company_name}}`. 7. Click **Save**. The variable counts toward the field's character limit as it is written, including the braces. The **Greeting message** allows 300 characters and the **Prompt** 20,000. ![ai-agent-variables-picker.png](https://cdn.document360.io/44ae307a-3737-4fbf-98e0-9b888deb90dc/Images/Documentation/ai-agent-variables-picker.png) ## Writing prompts with variables - **Keep the greeting safe.** The agent speaks the **Greeting message** almost word for word. Only use a variable there if every lead in the campaign has a value for it. - **Tell the agent what to do when a value is missing.** A lead may have no value for a field. For example: *"If the customer's first name is not provided, greet them without a name. Never guess a name, company, or amount."* - **Present values as facts in the prompt.** For example: *"The customer's current plan is `{{context_plan}}`. Their renewal date is `{{context_renewal_date}}`."* - **Check the result on a real call.** The **Test** panel does not fill in variables. To check them, run a short test Dialer campaign with a lead you control, then read the call's transcript in [Call Detail Records](/v1/docs/reporting-cdr). Template placeholders are not variables The **Receptionist**, **Support**, and **Outreach** prompt templates contain placeholders in double braces, such as `{{platform_or_brand}}` and `{{call_purpose}}`. They are not variables, Voiso does not fill them in, and it does not warn you about them when you save. Replace them with your own text. ## Related articles - [AI Agents](/v1/docs/ai-agents-ai-agents) - [Prompting guide](/v1/docs/prompting-guide) - [Interaction context mapping](/v1/docs/interaction-context-mapping) - [Dialer campaigns](/v1/docs/outbound-dialer-campaigns-overview)