> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tryhamsa.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Availability & Context

> Where variables are available in flow and single-prompt agents

Variable availability depends on **agent type** and **flow position**. The system uses flow analysis to decide which variables each node (or single prompt) can use.

## Availability by Variable Type

| Variable Type       | Global Nodes | Regular Nodes | Single-Prompt Agent | Logic                       |
| ------------------- | ------------ | ------------- | ------------------- | --------------------------- |
| System Variables    | ✅ Yes        | ✅ Yes         | ✅ Yes               | Always available            |
| Custom Variables    | ✅ Yes        | ✅ Yes         | ✅ Yes               | Always available            |
| Extracted Variables | ❌ No         | ✅ Yes\*       | ❌ No                | Only from predecessor nodes |
| Static Variables    | ❌ No         | ✅ Yes\*       | ❌ No                | Only from predecessor nodes |

\* Only if the current node runs **after** the node that created the variable.

## Flow Position Rules (Flow Agent)

1. **Predecessors only**: A node sees variables only from nodes that run before it.
2. **Execution paths**: All possible paths are considered when computing predecessors.
3. **Global nodes**: Nodes with `isGlobal: true` see only **system** and **custom** variables.
4. **Caching**: Availability is cached per node and refreshed when the flow changes.

## Example Flow

```
Start Node (creates: user_number)
  ↓
Conversation Node (creates: customer_name, appointment_date)
  ↓
Tool Node (creates: booking_id, confirmation_code)
  ↓
End Node

Available at each step:
- Start Node: system, custom
- Conversation Node: system, custom, user_number
- Tool Node: system, custom, user_number, customer_name, appointment_date
- End Node: system, custom, user_number, customer_name, appointment_date, booking_id, confirmation_code
```

## Single Prompt Agent Variables

Single prompt agents are standalone conversational agents that don't use the flow builder. They have a simplified variable model optimized for quick deployment and simple use cases.

### Variable Availability

| Variable Type       | Available | Notes                                  |
| ------------------- | --------- | -------------------------------------- |
| System Variables    | ✅ Yes     | All 15+ platform variables available   |
| Custom Variables    | ✅ Yes     | Converted to `params` in configuration |
| Extracted Variables | ❌ No      | No flow nodes to extract from          |
| Static Variables    | ❌ No      | No nodes to define static variables    |

### How Custom Variables Work in Single Prompt Agents

Custom variables in single prompt agents act as **parameters** that configure the agent:

**Definition (Variables Panel):**

```
Custom Variables:
- business_name: "Acme Corporation"
- support_email: "support@acme.com"
- max_conversation_turns: 10
- enable_transfers: true
```

**Conversion to params:**

```typescript theme={null}
// Custom variables become params in agent configuration
{
  params: {
    business_name: "Acme Corporation",
    support_email: "support@acme.com",
    max_conversation_turns: 10,
    enable_transfers: true
  }
}
```

**Usage in prompt:**

```
You are a customer service agent for {{business_name}}.
If customers need help, direct them to {{support_email}}.
Keep conversations under {{max_conversation_turns}} turns.
{{#if enable_transfers}}You can transfer calls to human agents.{{/if}}
```

### Key Differences from Flow Builder Agents

| Aspect           | Flow Builder Agents                  | Single Prompt Agents         |
| ---------------- | ------------------------------------ | ---------------------------- |
| Complexity       | Multi-node workflows                 | Single prompt configuration  |
| Variables        | System + Custom + Extracted + Static | System + Custom only         |
| Extraction       | AI extraction, toolpath, DTMF        | Not supported                |
| Flow Logic       | Conditional branching, loops         | Linear conversation          |
| Custom Variables | Workflow-level state                 | Configuration parameters     |
| Use Case         | Complex workflows                    | Simple conversational agents |

### Use Cases for Single Prompt Agents

**Good for:**

* Simple Q\&A agents
* Information lookup agents
* Basic customer service
* FAQ bots
* Quick prototypes
* Agents with minimal state

**Not good for:**

* Multi-step workflows
* Data collection and processing
* API integrations with variable extraction
* Complex conditional logic
* State management across multiple steps

### Configuration Example

**Variables Panel (Custom Variables):**

```
working_hours: "9 AM - 5 PM EST"
support_tier: "premium"
escalation_enabled: true
```

**Single Prompt Configuration:**

```
System Prompt:
You are {{agent_name}}, a helpful assistant.
Our working hours are {{working_hours}}.
Current time: {{current_time}}
Current date: {{current_date}}

Instructions:
- Be friendly and professional
- Answer questions about our products
{{#if escalation_enabled}}
- Offer to escalate complex issues to human agents
{{/if}}

User's phone: {{user_number}}
Call direction: {{direction}}
```

**Available variables in this example:**

* ✅ `working_hours`, `support_tier`, `escalation_enabled` (custom)
* ✅ `agent_name`, `current_time`, `current_date`, `user_number`, `direction` (system)

### When to Upgrade to Flow Builder

Consider upgrading to a Flow Builder agent when you need to:

* Extract data from conversations (AI extraction)
* Integrate with APIs and parse responses (toolpath extraction)
* Use conditional branching or multi-step logic
* Collect structured information across nodes
* Use DTMF capture or static variables

For DOs and DON'Ts specific to single prompt agents, see [Best Practices: Single Prompt Agent Variables](./best-practices#single-prompt-agent-variables).

## Variable Categories & Display

Variables are grouped for the UI:

| Category  | Icon | Contains                        |
| --------- | ---- | ------------------------------- |
| System    | 🔧   | Platform variables              |
| Custom    | ⚙️   | Workflow-level variables        |
| Extracted | 📤   | From nodes (AI, toolpath, DTMF) |
| Static    | 📌   | Node-level set values           |

Displayed per variable: **name**, **type**, **source** (for extracted/static), **description**, **default/example value**.

## Context-Aware Recommendations

The UI can suggest variables based on node type and content:

* **Conversation**: e.g. `customer_name`, `phone_number`, `appointment_date`, `issue_description`
* **Tool**: e.g. `api_response`, `status_code`, `response_data`, `error_message`
* **Transfer**: e.g. `transfer_reason`, `customer_context`, `conversation_summary`

See [UI Components & Validation](./ui-and-validation) for where these appear and [Introduction](./introduction) for the overall model.