Updated CI fix document (#8801)

* Add free-form object spec for testing purpose.

* Revert "Add free-form object spec for testing purpose."

This reverts commit b711d80.

* Updated ci-fix document.

Added how to run/fix model validation and semantic validation.

* Combined run locally and fix tips parts.

* Tweaked link text.

documentation/ci-fix.md

@@ -23,3 +23,24 @@ npm install; npm run prettier -- --write "specification/<service>/**/*.json"
 ```
 
 Then please commit and push changes made by prettier.
+
+## Model Validation
+
+Run Model Validation locally:
+```
+npm install -g oav
+oav validate-example <swagger-spec-path>
+```
+Please see [readme](https://github.com/Azure/oav/blob/master/README.md) for how to install or run tool in details.
+Or you can run it in [OpenAPI Hub](https://portal.azure-devex-tools.com/tools/static-validation/static/errors/default)
+Refer to [Semantic and Model Violations Reference](https://github.com/Azure/azure-rest-api-specs/blob/master/documentation/Semantic-and-Model-Violations-Reference.md) for detailed description of validations and how-to-fix guidance.
+
+## Semantic Validation
+Run Semantic Validation locally:
+```
+npm install -g oav
+oav validate-spec <swagger-spec-path>
+```
+Please see [readme](https://github.com/Azure/oav/blob/master/README.md) for how to install or run tool in details.
+Or you can run it in [OpenAPI Hub](https://portal.azure-devex-tools.com/tools/static-validation/static/errors/default)
+Refer to [Semantic and Model Violations Reference](https://github.com/Azure/azure-rest-api-specs/blob/master/documentation/Semantic-and-Model-Violations-Reference.md) for detailed description of validations and how-to-fix guidance.