Disclaimer: This is AI-generated, but I ran into this issue and tested the fix in prod. same in #34

Parity with Python upstream

The TypeScript port of RegisteredAction.promptDescription was JSON-stringifying zod's private _def AST, exposing internals like innerType/defaultValue/def to the LLM. Python upstream uses pydantic.BaseModel.model_json_schema() and avoids this entirely. This PR brings the TS implementation to parity by switching to z.toJSONSchema() (zod v4, already in the dep tree).

Reference: browser_use/tools/registry/views.py:31-56 on browser-use/browser-use main. Specifically views.py:33:

schema = self.param_model.model_json_schema()

Problem

For example, ScrollActionSchema was rendered to the LLM as:

{
  "down": {
    "type": "default",
    "innerType": { "def": { "type": "boolean" } },
    "defaultValue": true
  },
  "num_pages": {
    "type": "default",
    "innerType": { "def": { "type": "number" } },
    "defaultValue": 1
  }
}

This is wrong-tier information for the model: it shows zod internals rather than a parameter schema. Worse, the adjacency of "defaultValue": true (for down) right next to num_pages plausibly causes the model to copy the wrong default — we observed the model emitting num_pages: <boolean> repeatedly in real runs.

Fix

Switch promptDescription to render the param schema via z.toJSONSchema(...). The same ScrollActionSchema now renders as:

{
  "down": { "type": "boolean", "default": true },
  "num_pages": { "type": "number", "default": 1 }
}

Clean, standard, and unambiguous about which default belongs to which field.

Impact

In a downstream consumer (canary-env), this fix combined with the retry-feedback fix (#34) took an eval from "BA bails at step 5 with done(success=false) after a 3-fail cascade" to "BA completes at step 20 with run_complete".

Standalone effect of this PR: removes the _def cascade entirely. Residual num_pages: <boolean> errors still happen ~5x/run but now self-correct via retry feedback (#34).

Tests

• Added test/promptDescription.test.ts covering the JSON Schema rendering.
• Full suite: 968 pass / 0 fail.

Caveats

• The TS fix produces somewhat richer JSON Schema output than Python's terser name=type (description) per param. Open to matching the Python format if reviewers prefer.
• Relies on z.toJSONSchema from zod v4, which is already a dep. No new dependency.
• The prompt text the LLM sees changes shape — anything that was prompt-scraping the old _def dump will need to read JSON Schema instead. (We don't believe anything was; this was an internal accident, not a contract.)

🤖 Generated with Claude Code