As you edit your specification, Postman identifies syntax errors, such as wrong data types and nesting, and shows details about the errors so you can correct them. Postman also identifies API governance issues in OpenAPI specifications, based on the rules configured for your team.
Below the specification editor, Postman displays the validation pane in the Issues tab, which is selected by default. The validation pane has two sections: Syntax and Governance. Expand either section to view issues in your specification.
The validation pane only shows syntax errors and governance rule violations for the specification file you’re editing.
In the Postman footer, you can also check whether your specification has syntax errors or governance rule violations. If there are any issues, the footer shows the number of issues by severity. Click the error icon 
or warning icon 
to open the validation pane.
View syntax errors in your specification
Postman automatically identifies syntax errors as you edit your API specification. Errors can include missing fields, malformed field names, wrong data types, wrong nesting, or other issues. For Postman to be able to check your specification elements, you must use valid JSON or YAML.
To view any syntax errors, click Syntax in the validation pane. Each syntax error shows the number of times Postman found it in the specification, where the error occurs, details about the error, and the severity. Click a syntax error to go to its location in the specification.
If your specification is organized into multiple files and folders, every instance of the syntax error also has the path to its respective file. Click a syntax error to go to the file.
View rule violations in your specification
API Governance rule validation is available with Postman Enterprise plans.
As you edit your OpenAPI specification, Postman automatically checks it against the Postman API Governance rules configured for your team.
To view any governance rule violations, click Governance in the validation pane. Each rule violation shows the number of times Postman found it in the specification, where the rule violation occurs, details about the rule violation, and the severity. Click a governance rule violation to go to its location in the specification.
If your specification is organized into multiple files and folders, every instance of the rule violation will also have the path to its respective file. Click a governance rule violation to go to the file.
API Governance Managers can view detailed metrics on API Governance rule compliance in your specifications.