Summary
This guide explains how REST API action attributes work in Astra and how they are used within Astra agents. Attributes act as placeholders that store and pass data between instructions and actions.
You’ll learn the different types of attributes, how they behave, and how to use them correctly when configuring REST API (Representational State Transfer) actions.
Instructions
What is an attribute
In Astra, an attribute is a placeholder that stores a value. It allows your agent to dynamically use data during execution.
For example, attributes like first name or last name can store customer details and be reused in responses or actions.
Key points
Attributes act like variables inside your agent
They can be used in instructions and actions
In instructions, attributes are mainly used for clarity or structuring inputs and outputs
Input and output attributes
Attributes in Astra are categorized based on how they are used:
Input attributes
Provide data into an action or step
Example: passing a customer name into an API request
Output attributes
Store results returned from an action
Example: saving a response ID from an API
Both types can be referenced throughout your agent workflow.
A. Contact attributes
Contact attributes are a specific type of attribute linked to customer data.
Predefined contact attributes
Common examples include:
first namelast name
Custom contact attributes
You can create custom attributes based on your use case within the agent.
Important
Contact attributes only receive values when data is actually captured.
They are populated when:
A Custom form is submitted during the conversation
A REST API action is triggered after the conversation
Other important points to note
Contact attributes are not the same as contact fields
Contact fields include:
emailphone
They can also come from:
Custom forms
Lead qualification criteria
Contact attributes are linked to these fields only when data is captured through these flows.
B. Action attributes
Action attributes are tied to actions configured in your agent.
Types of action attributes
REST API action attributes
Predefined action attributes
1. Predefined action attributes
These become available when you add specific actions to your agent.
Examples:
Wati send sales summary →
sales_summary_content(input)Slack send message →
message_content(input)Google Sheets add row →
inserted_data_id(output)Google Sheets update row →
target_data_id(input)
2. REST API action attributes
Input attributes are created when you configure the action
Output attributes are generated after the action runs (during testing or live execution)
Important
You must add the corresponding action to your agent before using its attributes.
How to configure REST API action payload
REST API actions in Astra use placeholders to pass dynamic data.
What are placeholders
Placeholders are written using: {{placeholder_name}}
You can use them in:
Query parameters
Headers
Request body
Recommended method: use data input
This is the most flexible and recommended approach.
A. Using Data Input
Step 1: add a data input field
Create a data input in your action configuration.
Step 2: configure the field
Define:
Data type
Name
Description
Mandatory or optional
Reference attribute (optional)
Default value (optional)
Step 3: choose how the value is sourced
You have 3 options:
No reference
The agent generates the value from context
Add a clear description so the agent knows what to pass
Reference a contact attribute
Use only if the value is already captured
Avoid using this unless:
A custom form was submitted, or
A post-conversation API event occurred
Reference an action output attribute
Use output from a previous action
The referenced action must run before the current one
Step 4: use the placeholder
Reference it in your payload: {{data_input_name}}
Make sure the name matches exactly.
B. Using direct contact attribute
You can directly reference a contact attribute: {{contact.attribute_name}}
No need to define a data input
Can be inserted directly from the UI
C. Using direct action attribute
You can reference an action’s output: {{action.<action_id>#out#<attribute_name>}}
Links to output from a previous action
Can be inserted from the UI
No need to manually type the full format
Best practices
Use data input for most use cases
Avoid relying on contact attributes unless you are sure they are populated
Ensure action execution order is correct when using outputs
Test all API actions before deploying
By understanding Astra attributes, you can build more structured, reliable, and dynamic agents inside Wati.