#### ***Product/components** used and **version/fix** level:*
Edition: API Gateway Advanced Edition
Version: 10.15.0.2.143
#### *Detailed explanation of the problem:*
Header Constraints (Mandatory/Optional) mentioned as Method Parameters do not seem to take effect or doesn't seem to work while activating the HTTP Headers in ValidateAPISpecification in Request Policies.
#### *Error messages / **full error** message screenshot / **log** file:*
X-Callback-Url - Is set as optional parameter in method Parameter Definition.
Incase the Parameter is not send in the request from the client, it throws below exception.
{
"Exception": "API Gateway encountered an error. Error Message: API Specification validation failed. Required header is missing in the **Ocp-Apim-Subscription-Key.** Request Details: Service - transfer, Operation - /, Invocation Time:5:25:43 AM, Date:Nov 6, 2024, Client IP - 192.176.1.105, User - Default and Application:APIGWTestSubscription"
}
Though the Ocp-Apim-Subscription-Key key is present.
**Note:** Ocp-Apim-Subscription-Key is the equivalent of ApiKey field
#### *Question related to a **free trial**, or to a **production (customer)** instance?*
Production Instance