fix: resolve $ref references in tool input schema properties

client/src/components/ToolsTab.tsx

@@ -18,6 +18,7 @@ import {
   generateDefaultValue,
   isPropertyRequired,
   normalizeUnionType,
+  resolveRef,
 } from "@/utils/schemaUtils";
 import {
   CompatibilityCallToolResult,
@@ -90,14 +91,21 @@ const ToolsTab = ({
   useEffect(() => {
     const params = Object.entries(
       selectedTool?.inputSchema.properties ?? [],
-    ).map(([key, value]) => [
-      key,
-      generateDefaultValue(
+    ).map(([key, value]) => {
+      // First resolve any $ref references
+      const resolvedValue = resolveRef(
         value as JsonSchemaType,
-        key,
         selectedTool?.inputSchema as JsonSchemaType,
-      ),
-    ]);
+      );
+      return [
+        key,
+        generateDefaultValue(
+          resolvedValue,
+          key,
+          selectedTool?.inputSchema as JsonSchemaType,
+        ),
+      ];
+    });
     setParams(Object.fromEntries(params));
 
     // Reset validation errors when switching tools
@@ -154,7 +162,12 @@ const ToolsTab = ({
                 </p>
                 {Object.entries(selectedTool.inputSchema.properties ?? []).map(
                   ([key, value]) => {
-                    const prop = normalizeUnionType(value as JsonSchemaType);
+                    // First resolve any $ref references
+                    const resolvedValue = resolveRef(
+                      value as JsonSchemaType,
+                      selectedTool.inputSchema as JsonSchemaType,
+                    );
+                    const prop = normalizeUnionType(resolvedValue);
                     const inputSchema =
                       selectedTool.inputSchema as JsonSchemaType;
                     const required = isPropertyRequired(key, inputSchema);

client/src/utils/jsonUtils.ts

@@ -48,6 +48,7 @@ export type JsonSchemaType = {
   const?: JsonValue;
   oneOf?: (JsonSchemaType | JsonSchemaConst)[];
   anyOf?: (JsonSchemaType | JsonSchemaConst)[];
+  $ref?: string;
 };
 
 export type JsonObject = { [key: string]: JsonValue };

client/src/utils/schemaUtils.ts

@@ -145,6 +145,50 @@ export function isPropertyRequired(
   return schema.required?.includes(propertyName) ?? false;
 }
 
+/**
+ * Resolves $ref references in JSON schema
+ * @param schema The schema that may contain $ref
+ * @param rootSchema The root schema to resolve references against
+ * @returns The resolved schema without $ref
+ */
+export function resolveRef(
+  schema: JsonSchemaType,
+  rootSchema: JsonSchemaType,
+): JsonSchemaType {
+  if (!("$ref" in schema) || !schema.$ref) {
+    return schema;
+  }
+
+  const ref = schema.$ref;
+
+  // Handle simple #/properties/name references
+  if (ref.startsWith("#/")) {
+    const path = ref.substring(2).split("/");
+    let current: unknown = rootSchema;
+
+    for (const segment of path) {
+      if (
+        current &&
+        typeof current === "object" &&
+        current !== null &&
+        segment in current
+      ) {
+        current = (current as Record<string, unknown>)[segment];
+      } else {
+        // If reference cannot be resolved, return the original schema
+        console.warn(`Could not resolve $ref: ${ref}`);
+        return schema;
+      }
+    }
+
+    return current as JsonSchemaType;
+  }
+
+  // For other types of references, return the original schema
+  console.warn(`Unsupported $ref format: ${ref}`);
+  return schema;
+}
+
 /**
  * Normalizes union types (like string|null from FastMCP) to simple types for form rendering
  * @param schema The JSON schema to normalize