# Using JMESPath expressions Use **JMESPath expressions** to map and transform JSON response from webhook action into the desired data structure.

Example of using JMESPath expression in your output attributes mapping

Be aware of the following: * If your JMESPath expression is incorrect or points to non-existent fields, the output attribute value will be empty. * If the resulting value of your JMESPath does not match the target attribute type, the attribute value will also be empty. Resources on JMESPath: * [Official specification](https://jmespath.org/specification.html#jmespath-specification). * [Comprehensive examples](https://jmespath.org/examples.html). * [Tutorials](https://jmespath.org/tutorial.html). ### Examples **Custom function: `json_decode(...)`** Webhook V2 supports a custom JMESPath function called `json_decode(...)`. Use it when an API returns JSON **inside a string field** and you need to read values from that encoded object. Without `json_decode(...)`, string fields are treated as plain text and cannot be traversed with dot notation. **Syntax:** ``` json_decode() ``` You can combine it with normal JMESPath traversal, for example: ``` json_decode(payload).order.status ``` If the string is not valid JSON, the result is treated as empty for mapping purposes. **Example: extract values from a JSON-encoded field**
Input JSONJMESPath
{
  "eventId": "evt_901",
  "payload": "{\"order\":{\"id\":\"ORD-1007\",\"status\":\"shipped\",\"tracking\":{\"carrier\":\"DHL\",\"number\":\"TRK-7788\"}}}"
}

Expression:
json_decode(payload).order.tracking.number

Output:

TRK-7788
**Example: decode and return multiple fields**
Input JSONJMESPath
{
  "payload": "{\"order\":{\"id\":\"ORD-1007\",\"status\":\"shipped\"}}"
}

Expression:
{order_id: json_decode(payload).order.id, order_status: json_decode(payload).order.status}

Output:

{
  "order_id": "ORD-1007",
  "order_status": "shipped"
}
**Select a Single Field**
Input JSONJMESPath
{
  "name": "Alice",
  "age": 30,
  "city": "London"
}

Expression:
name

Output:

Alice
**Access Nested Fields**
Input JSONJMESPath
{
  "user": {
    "profile": {
      "name": "Charlie",
      "location": "London"
    }
  }
}

Expression:
user.profile.location

Output:

London
**Select Multiple Fields**
Input JSONJMESPath
{
  "id": 123,
  "name": "Bob",
  "email": "bob@example.com",
  "age": 25
}

Expression:
{name: name, email: email}

Output:

{
  "name": "Bob",
  "email": "bob@example.com"
}
**Select all array element's properties**
Input JSONJMESPath
{
  "products": [
    {"name": "Laptop", "price": 999},
    {"name": "Mouse", "price": 25},
    {"name": "Keyboard", "price": 75}
  ]
}

Expression:
products[*].name

Output:

[
  "Laptop",
  "Mouse",
  "Keyboard"
]
**Filter array by condition**
Input JSONJMESPath
{
  "items": [
    {"name": "Apple", "price": 1.5, "inStock": true},
    {"name": "Banana", "price": 0.8, "inStock": false},
    {"name": "Orange", "price": 2.0, "inStock": true}
  ]
}

Expression:
items[?inStock == `true`]

Output:

[
  {"name": "Apple", "price": 1.5, "inStock": true},
  {"name": "Orange", "price": 2.0, "inStock": true}
]
**Select root-level array**
Input JSONJMESPath
[
  {"id": 1, "name": "Alice", "role": "admin"},
  {"id": 2, "name": "Bob", "role": "user"},
  {"id": 3, "name": "Charlie", "role": "user"}
]

Expression:
@

Output:

[
  {"id": 1, "name": "Alice", "role": "admin"},
  {"id": 2, "name": "Bob", "role": "user"},
  {"id": 3, "name": "Charlie", "role": "user"}
]
**Use bult-in functions**
Input JSONJMESPath
{
  "items": [
    {"name": "Apple", "price": 15 },
    {"name": "Banana", "price": 999 },
    {"name": "Orange", "price": 75 }
  ]
}

Expression:
max(products[*].price)

Output:

999
#### Select array elements for a form message with dynamic data You can create [a from message with dynamic](https://docs.opendialog.ai/conversation-designer/message-design/message-types/form-message#creating-form-messages-with-dynamic-data) data retrieved from a webhook action. For example:
Input JSONJMESPath
{
  "products": [
    {"sku": "LAP-001", "name": "Laptop", "price": 999},
    {"sku": "MOU-002", "name": "Mouse", "price": 25},
    {"sku": "KEY-003", "name": "Keyboard", "price": 75}
  ]
}

Expression:
products[*].{key: sku, value: name}

Output:

[
  {"key": "LAP-001", "value": "Laptop"},
  {"key": "MOU-002", "value": "Mouse"},
  {"key": "KEY-003", "value": "Keyboard"}
]
This can then be used as a data source for your searchable select in a form message.