diff --git a/schema/config-schema.json b/schema/config-schema.json
index 94e88f3..ce13fcc 100644
--- a/schema/config-schema.json
+++ b/schema/config-schema.json
@@ -146,8 +146,19 @@
           },
           "toolUsage": {
             "type": "boolean"
+          },
+          "reward": {
+            "type": "boolean"
+          },
+          "languages": {
+            "type": "array",
+            "items": {
+              "type": "string",
+              "pattern": "^[a-z]{2}$"
+            }
           }
-        }
+        },
+        "additionalProperties": false
       },
       "Modality": {
         "type": "string",
diff --git a/schema/config_test.go b/schema/config_test.go
index fd6b644..391727a 100644
--- a/schema/config_test.go
+++ b/schema/config_test.go
@@ -474,6 +474,109 @@ func TestConfig(t *testing.T) {
     ]
   }
 }
+`,
+			fail: true,
+		},
+		// expected failure: reward is not boolean
+		{
+			config: `
+{
+  "descriptor": {
+    "name": "xyz-3-8B-Instruct",
+    "version": "3.1"
+  },
+  "config": {
+     "paramSize": "8b",
+     "capabilities": {
+        "inputTypes": ["text"],
+        "outputTypes": ["text"],
+        "reward": "true"
+     }
+  },
+  "modelfs": {
+    "type": "layers",
+    "diffIds": [
+       "sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
+    ]
+  }
+}
+`,
+			fail: true,
+		},
+		// expected failure: languages is not an array
+		{
+			config: `
+{
+  "descriptor": {
+    "name": "xyz-3-8B-Instruct",
+    "version": "3.1"
+  },
+  "config": {
+     "paramSize": "8b",
+     "capabilities": {
+        "inputTypes": ["text"],
+        "outputTypes": ["text"],
+        "languages": "en"
+     }
+  },
+  "modelfs": {
+    "type": "layers",
+    "diffIds": [
+       "sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
+    ]
+  }
+}
+`,
+			fail: true,
+		},
+		// expected failure: language code is not a two-letter ISO 639 code
+		{
+			config: `
+{
+  "descriptor": {
+    "name": "xyz-3-8B-Instruct",
+    "version": "3.1"
+  },
+  "config": {
+     "paramSize": "8b",
+     "capabilities": {
+        "inputTypes": ["text"],
+        "outputTypes": ["text"],
+        "languages": ["fra"]
+     }
+  },
+  "modelfs": {
+    "type": "layers",
+    "diffIds": [
+       "sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
+    ]
+  }
+}
+`,
+			fail: true,
+		},
+		// expected failure: unknown field in capabilities
+		{
+			config: `
+{
+  "descriptor": {
+    "name": "xyz-3-8B-Instruct",
+    "version": "3.1"
+  },
+  "config": {
+     "paramSize": "8b",
+     "capabilities": {
+        "inputTypes": ["text"],
+        "unknownField": true
+     }
+  },
+  "modelfs": {
+    "type": "layers",
+    "diffIds": [
+       "sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
+    ]
+  }
+}
 `,
 			fail: true,
 		},