hack to return tool call errors back to model

packages/opencode/src/tool/invalid.ts

@@ -0,0 +1,17 @@
+import { z } from "zod"
+import { Tool } from "./tool"
+
+export const InvalidTool = Tool.define("invalid", {
+  description: "Do not use",
+  parameters: z.object({
+    tool: z.string(),
+    error: z.string(),
+  }),
+  async execute(params) {
+    return {
+      title: "Invalid Tool",
+      output: `The arguments provided to the tool are invalid: ${params.error}`,
+      metadata: {},
+    }
+  },
+})

packages/opencode/src/tool/registry.ts

@@ -10,9 +10,11 @@ import { TaskTool } from "./task"
 import { TodoWriteTool, TodoReadTool } from "./todo"
 import { WebFetchTool } from "./webfetch"
 import { WriteTool } from "./write"
+import { InvalidTool } from "./invalid"
 
 export namespace ToolRegistry {
   const ALL = [
+    InvalidTool,
     BashTool,
     EditTool,
     WebFetchTool,