fix: Ensures final output tool is available when using vector tool search (#3701)

crates/goose/src/agents/agent.rs

@@ -372,7 +372,7 @@ impl Agent {
             || tool_call.name == ROUTER_LLM_SEARCH_TOOL_NAME
         {
             let selector = self.router_tool_selector.lock().await.clone();
-            let selected_tools = match selector.as_ref() {
+            let mut selected_tools = match selector.as_ref() {
                 Some(selector) => match selector.select_tools(tool_call.arguments.clone()).await {
                     Ok(tools) => tools,
                     Err(e) => {
@@ -394,6 +394,19 @@ impl Agent {
                     )
                 }
             };
+
+            // Append final_output tool if present (for structured output recipes, [Issue #3700](https://github.com/block/goose/issues/3700)
+            if let Some(final_output_tool) = self.final_output_tool.lock().await.as_ref() {
+                let tool = final_output_tool.tool();
+                let tool_content = Content::text(format!(
+                    "Tool: {}\nDescription: {}\nSchema: {}",
+                    tool.name,
+                    tool.description.unwrap_or_default(),
+                    serde_json::to_string_pretty(&tool.input_schema).unwrap_or_default()
+                ));
+                selected_tools.push(tool_content);
+            }
+
             ToolCallResult::from(Ok(selected_tools))
         } else {
             // Clone the result to ensure no references to extension_manager are returned