Merge pull request modelcontextprotocol#519 from modelcontextprotocol/basil/tighten_output_schema

Tighten Tool.outputSchema

Author: bhosmer-ant

schema/draft/schema.json

@@ -2128,9 +2128,30 @@
                     "type": "string"
                 },
                 "outputSchema": {
-                    "additionalProperties": true,
                     "description": "An optional JSON Schema object defining the structure of the tool's output.\n\nIf set, a CallToolResult for this Tool MUST contain a structuredContent field whose contents validate against this schema.\nIf not set, a CallToolResult for this Tool MUST contain a content field.",
-                    "properties": {},
+                    "properties": {
+                        "properties": {
+                            "additionalProperties": {
+                                "additionalProperties": true,
+                                "properties": {},
+                                "type": "object"
+                            },
+                            "type": "object"
+                        },
+                        "required": {
+                            "items": {
+                                "type": "string"
+                            },
+                            "type": "array"
+                        },
+                        "type": {
+                            "const": "object",
+                            "type": "string"
+                        }
+                    },
+                    "required": [
+                        "type"
+                    ],
                     "type": "object"
                 }
             },

schema/draft/schema.ts

@@ -853,7 +853,11 @@ export interface Tool {
    * If set, a CallToolResult for this Tool MUST contain a structuredContent field whose contents validate against this schema.
    * If not set, a CallToolResult for this Tool MUST contain a content field.
    */
-  outputSchema?: object;
+  outputSchema?: {
+    type: "object";
+    properties?: { [key: string]: object };
+    required?: string[];
+  };
 
   /**
    * Optional additional tool information.