diff --git a/src/objective-c/GRPCClient/GRPCCall.h b/src/objective-c/GRPCClient/GRPCCall.h
index f4d1838da79be04c62ade11834682e276b59a4ce..c9b6e6d6e23bebe1a70f663f33005f5dcfb67dd0 100644
--- a/src/objective-c/GRPCClient/GRPCCall.h
+++ b/src/objective-c/GRPCClient/GRPCCall.h
@@ -55,6 +55,13 @@
 extern id const kGRPCHeadersKey;
 extern id const kGRPCTrailersKey;
 
+// The container of the request headers of an RPC conforms to this protocol, which is a subset of
+// NSMutableDictionary's interface. It will become a NSMutableDictionary later on.
+// The keys of this container are the header names, which per the HTTP standard are case-
+// insensitive. They are stored in lowercase (which is how HTTP/2 mandates them on the wire), and
+// can only consist of ASCII characters.
+// A header value is a NSString object (with only ASCII characters), unless the header name has the
+// suffix "-bin", in which case the value has to be a NSData object.
 @protocol GRPCRequestHeaders <NSObject>
 
 @property(nonatomic, readonly) NSUInteger count;
diff --git a/src/objective-c/GRPCClient/private/GRPCRequestHeaders.h b/src/objective-c/GRPCClient/private/GRPCRequestHeaders.h
index 066f71a8f6af80b0e93574100d060a3a0494cafa..1391b5725f14eee0f175f2d16245dd490c53bf58 100644
--- a/src/objective-c/GRPCClient/private/GRPCRequestHeaders.h
+++ b/src/objective-c/GRPCClient/private/GRPCRequestHeaders.h
@@ -47,6 +47,6 @@
 - (void)setObject:(id)obj forKeyedSubscript:(NSString *)key;
 
 - (void)removeAllObjects;
-- (void)removeObjectForKey:(NSString *)aKey;
+- (void)removeObjectForKey:(NSString *)key;
 
-@end
\ No newline at end of file
+@end
diff --git a/src/objective-c/GRPCClient/private/GRPCRequestHeaders.m b/src/objective-c/GRPCClient/private/GRPCRequestHeaders.m
index d4bbbdf84a33e3d177aec1353dee737e91d3fc34..d0d8de89a13ac9eeb9e004b47181f713cf1c1857 100644
--- a/src/objective-c/GRPCClient/private/GRPCRequestHeaders.m
+++ b/src/objective-c/GRPCClient/private/GRPCRequestHeaders.m
@@ -117,4 +117,4 @@ static void CheckKeyValuePairIsValid(NSString *key, id value) {
 - (grpc_metadata *)grpc_metadataArray {
   return _proxy.grpc_metadataArray;
 }
-@end
\ No newline at end of file
+@end