diff --git a/sdk/lib/async/stream.dart b/sdk/lib/async/stream.dart
index cdb8211cc66..ed95a05b7f2 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -689,7 +689,7 @@ abstract class Stream<T> {
   }
 
   /**
-   * Applies  [streamTransformer] to this stream.
+   * Applies [streamTransformer] to this stream.
    *
    * Returns the transformed stream,
    * that is, the result of `streamTransformer.bind(this)`.
diff --git a/sdk/lib/convert/json.dart b/sdk/lib/convert/json.dart
index a834a9e633e..1fa356d705c 100644
--- a/sdk/lib/convert/json.dart
+++ b/sdk/lib/convert/json.dart
@@ -181,6 +181,9 @@ class JsonCodec extends Codec<Object, String> {
 }
 
 /// This class converts JSON objects to strings.
+///
+/// When used as a [StreamTransformer], this converter does not promise
+/// that the input object is emitted as a single string event.
 class JsonEncoder extends Converter<Object, String> {
   /// The string used for indention.
   ///
@@ -470,7 +473,14 @@ class _JsonUtf8EncoderSink extends ChunkedConversionSink<Object> {
   }
 }
 
-/// This class parses JSON strings and builds the corresponding objects.
+/// This class parses JSON strings and builds the corresponding value.
+///
+/// A JSON input must be the JSON encoding of a single JSON value,
+/// which can be a list or map containing other values.
+///
+/// When used as a [StreamTransformer], the input stream may emit
+/// multiple strings. The concatenation of all of these strings must
+/// be a valid JSON encoding of a single JSON value.
 class JsonDecoder extends Converter<String, Object> {
   final Function(Object key, Object value) _reviver;
 
diff --git a/sdk_nnbd/lib/async/stream.dart b/sdk_nnbd/lib/async/stream.dart
index c4ee2f28411..565b9f49a26 100644
--- a/sdk_nnbd/lib/async/stream.dart
+++ b/sdk_nnbd/lib/async/stream.dart
@@ -668,7 +668,7 @@ abstract class Stream<T> {
   }
 
   /**
-   * Applies  [streamTransformer] to this stream.
+   * Applies [streamTransformer] to this stream.
    *
    * Returns the transformed stream,
    * that is, the result of `streamTransformer.bind(this)`.
diff --git a/sdk_nnbd/lib/convert/json.dart b/sdk_nnbd/lib/convert/json.dart
index a75dbb57f46..95286027255 100644
--- a/sdk_nnbd/lib/convert/json.dart
+++ b/sdk_nnbd/lib/convert/json.dart
@@ -473,6 +473,13 @@ class _JsonUtf8EncoderSink extends ChunkedConversionSink<Object?> {
 }
 
 /// This class parses JSON strings and builds the corresponding objects.
+///
+/// A JSON input must be the JSON encoding of a single JSON value,
+/// which can be a list or map containing other values.
+///
+/// When used as a [StreamTransformer], the input stream may emit
+/// multiple strings. The concatenation of all of these strings must
+/// be a valid JSON encoding of a single JSON value.
 class JsonDecoder extends Converter<String, Object?> {
   final Object? Function(Object? key, Object? value)? _reviver;