Fix Anthropic provider tool format to use custom nested object

Author: bhouston

packages/agent/src/core/llm/providers/anthropic.ts

@@ -81,9 +81,11 @@ export class AnthropicProvider implements LLMProvider {
       if (functions && functions.length > 0) {
         (requestOptions as any).tools = functions.map(fn => ({
           type: 'custom',
-          name: fn.name,
-          description: fn.description,
-          input_schema: fn.parameters,
+          custom: {
+            name: fn.name,
+            description: fn.description,
+            input_schema: fn.parameters,
+          }
         }));
       }