## Problem
Using an AI Agent step in a workflow fails with:
> Invalid schema for function 'navigate_app': schema must be a JSON
Schema of 'type: "object"', got 'type: "None"'.
## Root cause
The `navigate_app` tool declared its `inputSchema` as a top-level
`z.discriminatedUnion('type', [...])`. When serialized via
`toToolJsonSchema`, a discriminated union produces a **root-level
`anyOf`** with no top-level `"type"`:
```json
{ "anyOf": [ { "type": "object", ... }, ... ] }
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Etienne
02d62c4175
