diff --git a/UpsilonLanguageServer/Lib/Upsilon.dll b/UpsilonLanguageServer/Lib/Upsilon.dll
index 9a7cb8b..f32e9b1 100644
Binary files a/UpsilonLanguageServer/Lib/Upsilon.dll and b/UpsilonLanguageServer/Lib/Upsilon.dll differ
diff --git a/UpsilonLanguageServer/Lib/Upsilon.pdb b/UpsilonLanguageServer/Lib/Upsilon.pdb
index 8d0f737..8d20367 100644
Binary files a/UpsilonLanguageServer/Lib/Upsilon.pdb and b/UpsilonLanguageServer/Lib/Upsilon.pdb differ
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/BoundTypeParser.cs b/UpsilonLanguageServer/UpsilonLanguageServer/BoundTypeParser.cs
index a3ac5ad..a4e933d 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/BoundTypeParser.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/BoundTypeParser.cs
@@ -120,12 +120,14 @@ namespace UpsilonLanguageServer
                         foreach (var prop in properties)
                         {
                             var parameterValue = (JObject) prop.Value;
+                            var parName = parameterValue.GetValue("name", StringComparison.InvariantCultureIgnoreCase)
+                                ?.ToString();
                             var parType = parameterValue.GetValue("type", StringComparison.InvariantCultureIgnoreCase)
                                 ?.ToString();
                             var parsedType = ParseType(parType);
                             var isOptional = parameterValue.GetValue("IsOptional", StringComparison.InvariantCultureIgnoreCase)
                                 ?.ToObject<bool>();
-                            parameters.Add(new InternalFunctionVariableSymbol.InternalFunctionParameter(parsedType,
+                            parameters.Add(new InternalFunctionVariableSymbol.InternalFunctionParameter(parName, parsedType,
                                 isOptional.HasValue && isOptional.Value));
                         }
                     }
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/DiagnosticsProvider.cs b/UpsilonLanguageServer/UpsilonLanguageServer/DiagnosticsProvider.cs
index dfe004c..dcc2234 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/DiagnosticsProvider.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/DiagnosticsProvider.cs
@@ -33,6 +33,7 @@ namespace UpsilonLanguageServer
             var task = RealLint(document, maxNumberOfProblems, session, content, diag);
             // either wait until the script is linted, or until a second has passed (timeout)
             await Task.WhenAny(task, Task.Delay(1000));
+            session.IsChanging = false;
             return diag;
         }
 
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/LanguageServerSession.cs b/UpsilonLanguageServer/UpsilonLanguageServer/LanguageServerSession.cs
index b61cde6..7b5b621 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/LanguageServerSession.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/LanguageServerSession.cs
@@ -71,9 +71,11 @@ namespace UpsilonLanguageServer
 
         public BoundScript Bound { get; set; }
         public SourceText SourceText { get; set; }
+        public bool IsChanging { get; set; }
 
         public void NotifyChanges(IEnumerable<TextDocumentContentChangeEvent> changes)
         {
+            IsChanging = true;
             lock (_syncLock)
             {
                 if (_impendingChanges == null)
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/Services/InitializationService.cs b/UpsilonLanguageServer/UpsilonLanguageServer/Services/InitializationService.cs
index 359b683..0524393 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/Services/InitializationService.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/Services/InitializationService.cs
@@ -34,7 +34,7 @@ namespace UpsilonLanguageServer.Services
             return new InitializeResult(new ServerCapabilities
             {
                 HoverProvider         = true,
-                SignatureHelpProvider = new SignatureHelpOptions("()"),
+                SignatureHelpProvider = new SignatureHelpOptions( new[]{'(', ','}),
                 CompletionProvider    = new CompletionOptions(true, ""),
                 TextDocumentSync = new TextDocumentSyncOptions
                 {
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/Services/TextDocumentServer.cs b/UpsilonLanguageServer/UpsilonLanguageServer/Services/TextDocumentServer.cs
index 060ecca..062a14c 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/Services/TextDocumentServer.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/Services/TextDocumentServer.cs
@@ -66,12 +66,37 @@ namespace UpsilonLanguageServer.Services
         }
 
         [JsonRpcMethod]
-        public SignatureHelp SignatureHelp(TextDocumentIdentifier textDocument, Position position)
+        public async Task<SignatureHelp> SignatureHelp(TextDocumentIdentifier textDocument, Position position)
         {
-            // TODO
-            return new SignatureHelp(new List<SignatureInformation>
+            if (Session.Documents.TryGetValue(textDocument.Uri, out var doc))
             {
-            });
+                await doc.WaitForDocumentBound();
+                if (doc.Bound != null && doc.SourceText != null)
+                {
+                    var linePos  = doc.SourceText.GetLineStartPos(position.Line);
+                    var findNode = doc.Bound.GetBottomNodeAtPosition(linePos + position.Character);
+                    if (findNode != null)
+                    {
+                        if (findNode.Kind == BoundKind.BoundFunctionCallExpression)
+                        {
+                            var functionCall = (BoundFunctionCallExpression)findNode;
+                            var exp = Binder.ResolveVariable(functionCall.Identifier, null);
+                            if (exp is InternalFunctionVariableSymbol internalFunction)
+                            {
+                                var n = new SignatureHelp(new List<SignatureInformation>()
+                                {
+                                    new SignatureInformation(exp.Name, string.Join("   \n", exp.CommentValue),
+                                        internalFunction.FunctionParameters.Select(
+                                            x => new ParameterInformation("", $"{x.Name} ({x.ValidTypes})")).ToList())
+                                }, 0, functionCall.Parameters.Length);
+                                return n;
+                            }
+                        }
+                    }
+                }
+            }
+
+            return new SignatureHelp();
         }
 
         [JsonRpcMethod(IsNotification = true)]
diff --git a/UpsilonLanguageServer/UpsilonLanguageServer/Utility.cs b/UpsilonLanguageServer/UpsilonLanguageServer/Utility.cs
index 483e8d4..e464834 100644
--- a/UpsilonLanguageServer/UpsilonLanguageServer/Utility.cs
+++ b/UpsilonLanguageServer/UpsilonLanguageServer/Utility.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Threading.Tasks;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 
@@ -15,5 +16,13 @@ namespace UpsilonLanguageServer
         {
             return DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff");
         }
+
+        public static async Task WaitForDocumentBound(this SessionDocument doc)
+        {
+            while (doc.IsChanging)
+            {
+                await Task.Delay(20);
+            }
+        }
     }
 }
\ No newline at end of file