custom tool with plain-object args silently fails to register

Description

A custom tool whose args are a plain JS object (not a Zod schema) never registers, and no error or warning is printed. tool() expects z.ZodRawShape (packages/plugin/src/tool.ts:45); a plain object is neither coerced nor rejected — it's silently dropped. Expected: either accept a plain JSON-schema object, or emit a clear "args must be a Zod schema" error at registration.

Workaround: use a Zod schema for args.

Plugins

none

OpenCode version

1.18.16

Steps to reproduce

1. Define a custom tool in .opencode/tools/ with args as a plain object,
   e.g. args: { foo: "string" }.
2. Start OpenCode (or run headless).
3. The tool is absent from the tool list with no diagnostic message.

Screenshot and/or share link

No response

Operating System

Ubuntu 24.04 (aarch64)

Terminal

non-interactive (openshell sandbox exec -- sh -c, --no-tty)