VAP-3952 added kb reference url (#247)

Author: ramsrib

fern/knowledge-base/knowledge-base.mdx

@@ -115,5 +115,7 @@ By following these guidelines, you can create a comprehensive Knowledge Base tha
 
 <Info>
   Currently, Vapi's Knowledge Base functionality supports Google as a provider
-  with the gemini-1.5-flash model for knowledge retrieval.
+  with the gemini-1.5-flash model for knowledge retrieval. For the most
+  up-to-date information on supported providers and models, please refer to our
+  [API documentation](api-reference/tools/create#request.body.query.knowledgeBases).
 </Info>