diff --git a/schema/klighd/SKGraphSchema.json b/schema/klighd/SKGraphSchema.json
index 5305f351..8e38b258 100644
--- a/schema/klighd/SKGraphSchema.json
+++ b/schema/klighd/SKGraphSchema.json
@@ -3,6 +3,7 @@
     "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "SKElement",
     "type": "object",
+    "required": ["data", "properties", "type"],
     "properties": {
         "data": {
             "type": "array",
@@ -24,6 +25,7 @@
     "definitions": {
         "SModelElement": {
             "type": "object",
+            "required": ["type", "id", "children"],
             "properties": {
                 "type": {
                     "type": "string"
@@ -47,6 +49,7 @@
         },
         "SShapeElement": {
             "allOf": [{"$ref": "#/definitions/SModelElement"}],
+            "required": ["size"],
             "properties": {
                 "size": {
                     "type": "object",
@@ -65,6 +68,7 @@
         },
         "SKGraph": {
             "allOf": [{"$ref": "#"}, {"$ref": "#/definitions/SModelElement"}],
+            "required": ["type", "revision"],
             "properties": {
                 "type": {
                     "type": "string",
@@ -77,6 +81,7 @@
         },
         "SKNode": {
             "allOf": [{"$ref": "#"}, {"$ref": "#/definitions/SShapeElement"}],
+            "required": ["type"],
             "properties": {
                 "type": {
                     "type": "string",
@@ -86,6 +91,7 @@
         },
         "SKLabel": {
             "allOf": [{"$ref": "#"}, {"$ref": "#/definitions/SModelElement"}],
+            "required": ["type", "text"],
             "properties": {
                 "text": {
                     "type": "string"
@@ -98,6 +104,7 @@
         },
         "SKEdge": {
             "allOf": [{"$ref": "#"}, {"$ref": "#/definitions/SModelElement"}],
+            "required": ["type", "sourceId", "targetId"],
             "properties": {
                 "sourceId": {
                     "type": "string"
diff --git a/schema/klighd/actions/setSyntheses.json b/schema/klighd/actions/setSyntheses.json
index 021faf00..37aae4a3 100644
--- a/schema/klighd/actions/setSyntheses.json
+++ b/schema/klighd/actions/setSyntheses.json
@@ -4,6 +4,7 @@
     "title": "setSyntheses",
     "type": "object",
     "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/action.json"}],
+    "required": ["kind", "syntheses"],
     "properties": {
         "kind": {
             "type": "string",
@@ -19,6 +20,7 @@
     "definitions": {
         "synthesis": {
             "type": "object",
+            "required": ["id", "displayName"],
             "properties": {
                 "id": {
                     "type": "string"
diff --git a/schema/klighd/actions/updateOptions.json b/schema/klighd/actions/updateOptions.json
index 3a2b6f39..b570d319 100644
--- a/schema/klighd/actions/updateOptions.json
+++ b/schema/klighd/actions/updateOptions.json
@@ -4,6 +4,7 @@
     "title": "updateOptions",
     "type": "object",
     "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/action.json"}],
+    "required": ["kind", "valuedSynthesisOptions", "layoutOptions", "actions", "modelUri"],
     "properties": {
         "kind": {
             "type": "string",
@@ -28,6 +29,7 @@
     "definitions": {
         "ValuedSynthesisOption": {
             "type": "object",
+            "required": ["synthesisOption", "currentValue"],
             "properties": {
                 "synthesisOption": {
                     "anyOf": [
@@ -46,8 +48,8 @@
         },
         "SynthesisOption": {
             "type": "object",
+            "required": ["id", "name", "type", "sourceHash", "initialValue"],
             "properties": {
-                        
                 "id": {
                     "type": "string"
                 },
@@ -55,7 +57,8 @@
                     "type": "string"
                 },
                 "type": {
-                    "type": "number"
+                    "type": "number",
+                    "enum": [0, 1, 2, 3, 4, 5]
                 },
                 "updateAction": {
                     "type": "string"
@@ -83,6 +86,7 @@
         },
         "choiceSynthesisOption": {
             "allOf": [{"$ref": "#/definitions/SynthesisOption"}],
+            "required": ["values"],
             "properties": {
                 "type": {
                     "type": "number",
@@ -101,6 +105,7 @@
         },
         "rangeSynthesisOption": {
             "allOf": [{"$ref": "#/definitions/SynthesisOption"}],
+            "required": ["range", "stepSize"],
             "properties": {
                 "type": {
                     "type": "number",
diff --git a/schema/klighd/messages/setPreferences.json b/schema/klighd/messages/setPreferences.json
index 75a37b7a..75c6b943 100644
--- a/schema/klighd/messages/setPreferences.json
+++ b/schema/klighd/messages/setPreferences.json
@@ -2,17 +2,16 @@
     "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/klighd/messages/setPreferences.json",
     "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "keith/preferences/setPreferences",
-    "type": "object",
+    "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/requestMessage.json"}],
+    "required": ["method", "params"],
     "properties": {
-        "jsonrpc": {
-            "type": "string"
-        },
         "method": {
             "type": "string",
             "enum": ["keith/preferences/setPreferences"]
         },
         "params": {
             "type": "object",
+            "required": ["diagram.shouldSelectDiagram", "diagram.shouldSelectText", "diagram.incrementalDiagramGenerator"],
             "properties": {
                 "diagram.shouldSelectDiagram": {
                     "type": "boolean"
diff --git a/schema/lsp/initialize.json b/schema/lsp/initialize.json
index 8d9f2e8d..ae7b5766 100644
--- a/schema/lsp/initialize.json
+++ b/schema/lsp/initialize.json
@@ -2,14 +2,9 @@
     "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/lsp/initialize.json",
     "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "initialize",
-    "type": "object",
+    "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/lsp/requestMessage.json"}],
+    "required": ["method", "params"],
     "properties": {
-        "jsonrpc": {
-            "type": "string"
-        },
-        "id": {
-            "type": "number"
-        },
         "method": {
             "type": "string",
             "enum": ["initialize"]
diff --git a/schema/lsp/message.json b/schema/lsp/message.json
new file mode 100644
index 00000000..ef38af37
--- /dev/null
+++ b/schema/lsp/message.json
@@ -0,0 +1,13 @@
+{
+    "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/lsp/message.json",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "message",
+    "type": "object",
+    "required": ["jsonrpc"],
+    "properties": {
+        "jsonrpc": {
+            "type": "string",
+            "enum": ["2.0"]
+        }
+    }
+}
\ No newline at end of file
diff --git a/schema/lsp/requestMessage.json b/schema/lsp/requestMessage.json
new file mode 100644
index 00000000..1fa41a01
--- /dev/null
+++ b/schema/lsp/requestMessage.json
@@ -0,0 +1,19 @@
+{
+    "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/lsp/requestmessage.json",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "message",
+    "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/lsp/message.json"}],
+    "required": ["id", "method"],
+    "properties": {
+        "id": {
+            "type": ["number", "string"]
+        },
+        "method": {
+            "type": "string",
+            "enum": ["requestMessage"]
+        },
+        "params": {
+            "type": ["array", "object"]
+        }
+    }
+}
\ No newline at end of file
diff --git a/schema/lsp/responseMessage.json b/schema/lsp/responseMessage.json
new file mode 100644
index 00000000..48db567e
--- /dev/null
+++ b/schema/lsp/responseMessage.json
@@ -0,0 +1,15 @@
+{
+    "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/lsp/requestmessage.json",
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "message",
+    "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/lsp/message.json"}],
+    "required": ["id"],
+    "oneOf": [{"required": ["result"]}, {"required": ["error"]}],
+    "properties": {
+        "id": {
+            "type": ["number", "string", "null"]
+        },
+        "result": {},
+        "error": {}
+    }
+}
\ No newline at end of file
diff --git a/schema/sprotty/actions/action.json b/schema/sprotty/actions/action.json
index 48f6c51b..067295b0 100644
--- a/schema/sprotty/actions/action.json
+++ b/schema/sprotty/actions/action.json
@@ -3,6 +3,7 @@
     "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "action",
     "type": "object",
+    "required": ["kind"],
     "properties": {
         "kind": {
             "type": "string"
diff --git a/schema/sprotty/actions/requestBounds.json b/schema/sprotty/actions/requestBounds.json
index 8eb97ad9..9ad3dd50 100644
--- a/schema/sprotty/actions/requestBounds.json
+++ b/schema/sprotty/actions/requestBounds.json
@@ -4,31 +4,14 @@
     "title": "requestBounds",
     "type": "object",
     "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/actions/action.json"}],
+    "required": ["kind", "newRoot"],
     "properties": {
         "kind": {
             "type": "string",
             "enum": ["requestBounds"]
         },
         "newRoot": {
-            "type": "object",
-            "properties": {
-                "properties": {},
-                "revision": {
-                    "type": "number"
-                },
-                "type": {
-                    "type": "string"
-                },
-                "id": {
-                    "type": "string"
-                },
-                "children": {
-                    "type": "array",
-                    "items": {
-                        "$ref": "/kieler/klighd-vscode/tree/main/schema/klighd/SKGraphSchema#/definitions/SKGraph"
-                    }
-                }
-            }
+            "$ref": "/kieler/klighd-vscode/tree/main/schema/klighd/SKGraphSchema#/definitions/SKGraph"
         }
     }
 }
\ No newline at end of file
diff --git a/schema/sprotty/actions/requestModel.json b/schema/sprotty/actions/requestModel.json
index f9e1564f..1aebcb5b 100644
--- a/schema/sprotty/actions/requestModel.json
+++ b/schema/sprotty/actions/requestModel.json
@@ -4,31 +4,32 @@
     "title": "requestBounds",
     "type": "object",
     "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/actions/action.json"}],
-        "properties": {
-            "kind": {
-                "type": "string",
-                "enum": ["requestModel"]
-            },
-            "options": {
-                "type": "object",
-                "properties": {
-                    "needsClientLayout": {
-                        "type": "boolean"
-                    },
-                    "needsServerLayout": {
-                        "type": "boolean"
-                    },
-                    "sourceUri": {
-                        "type": "string"
-                    },
-                    "diagramType": {
-                        "type": "string",
-                        "enum": ["keith-diagram"]
-                    }
+    "required": ["kind", "options", "requestId"],
+    "properties": {
+        "kind": {
+            "type": "string",
+            "enum": ["requestModel"]
+        },
+        "options": {
+            "type": "object",
+            "properties": {
+                "needsClientLayout": {
+                    "type": "boolean"
+                },
+                "needsServerLayout": {
+                    "type": "boolean"
+                },
+                "sourceUri": {
+                    "type": "string"
+                },
+                "diagramType": {
+                    "type": "string",
+                    "enum": ["keith-diagram"]
                 }
-            },
-            "requestId": {
-                "type": "string"
             }
+        },
+        "requestId": {
+            "type": "string"
         }
+    }
 }
\ No newline at end of file
diff --git a/schema/sprotty/diagramAccept.json b/schema/sprotty/diagramAccept.json
index 8af36a81..531bb740 100644
--- a/schema/sprotty/diagramAccept.json
+++ b/schema/sprotty/diagramAccept.json
@@ -2,17 +2,16 @@
     "$id": "https://github.com/kieler/klighd-vscode/tree/main/schema/sprotty/messages/diagramAccept.json",
     "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "diagram/accept",
-    "type": "object",
+    "allOf": [{"$ref": "/kieler/klighd-vscode/tree/main/schema/sprotty/requestMessage.json"}],
+    "required": ["method", "params"],
     "properties": {
-        "jsonrpc": {
-            "type": "string"
-        },
         "method": {
             "type": "string",
             "enum": ["diagram/accept"]
         },
         "params": {
             "type": "object",
+            "required": ["clientId", "action"],
             "properties": {
                 "clientId": {
                     "type": "string",