docs(validation): fix broken link; enrich built-in jmespath links

docs/utilities/validation.md

@@ -194,7 +194,7 @@ For each format defined in a dictionary key, you must use a regex, or a function
 
 You might have events or responses that contain non-encoded JSON, where you need to decode before validating them.
 
-You can use our built-in [JMESPath functions](/utilities/jmespath_functions) within your expressions to do exactly that to decode JSON Strings, base64, and uncompress gzip data.
+You can use our built-in [JMESPath functions](./jmespath_functions.md) within your expressions to do exactly that to [deserialize JSON Strings](./jmespath_functions.md#powertools_json-function), [decode base64](./jmespath_functions.md#powertools_base64-function), and [decompress gzip data](./jmespath_functions.md#powertools_base64_gzip-function).
 
 ???+ info
-    We use these for built-in envelopes to easily to decode and unwrap events from sources like Kinesis, CloudWatch Logs, etc.
+    We use these for [built-in envelopes](#built-in-envelopes) to easily to decode and unwrap events from sources like Kinesis, CloudWatch Logs, etc.