hermes-agent/tools/computer_use/schema.py
briandevans 280dd4513a fix(computer-use): address Copilot review on max_elements cap
Four findings from Copilot's review on PR #22891, all in the AX
elements-array cap added by 22fa1ed:

1. The truncation note ("response truncated to N of M elements") was
   appended unconditionally — including in the som/vision multimodal
   path, whose response carries a screenshot rather than an `elements`
   array. The note described a payload field that wasn't present.
   Moved the note into the AX-text branch where the array actually
   appears.

2. `_format_elements(cap.elements)` ran on the full untrimmed list with
   its own `max_lines=40` cap, so a caller passing `max_elements=10`
   would see summary lines referencing `#11..#40` even though the JSON
   `elements` array only held #1..#10. Format on `visible_elements`
   instead so the summary indices always exist in the response.

3. `_coerce_max_elements` enforced a lower bound but no upper bound,
   so `max_elements=10_000_000` silently disabled the safeguard and
   reintroduced the original context-blow-up. Added a hard cap
   (`_MAX_ALLOWED_MAX_ELEMENTS = 1000`) that clamps oversized values.

4. The schema string said "Default 100" but the property carried no
   `default` field, and claimed `max_elements` had no effect on som/
   vision while the image-missing fallback path can still return an
   elements array. Added `"default": 100`, `"maximum": 1000`, and
   clarified the fallback-path wording.

Each finding gets a regression test:

- test_capture_ax_clamps_oversized_max_elements_to_hard_cap
- test_capture_ax_summary_indices_match_returned_elements
- test_capture_multimodal_summary_omits_truncation_note
- test_schema_max_elements_documents_default_and_upper_bound

Verified with `pytest tests/tools/test_computer_use.py` (53 passed,
including the 5 new cases). Confirmed each new test fails on the
pre-fix code path before applying the production change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-21 19:07:32 -07:00

213 lines
9.7 KiB
Python

"""Schema for the generic `computer_use` tool.
Model-agnostic. Any tool-calling model can drive this. Vision-capable models
should prefer `capture(mode='som')` then `click(element=N)` — much more
reliable than pixel coordinates. Pixel coordinates remain supported for
models that were trained on them (e.g. Claude's computer-use RL).
"""
from __future__ import annotations
from typing import Any, Dict
# One consolidated tool with an `action` discriminator. Keeps the schema
# compact and the per-turn token cost low.
COMPUTER_USE_SCHEMA: Dict[str, Any] = {
"name": "computer_use",
"description": (
"Drive the macOS desktop in the background — screenshots, mouse, "
"keyboard, scroll, drag — without stealing the user's cursor, "
"keyboard focus, or Space. Preferred workflow: call with "
"action='capture' (mode='som' gives numbered element overlays), "
"then click by `element` index for reliability. Pixel coordinates "
"are supported for models trained on them. Works on any window — "
"hidden, minimized, on another Space, or behind another app. "
"macOS only; requires cua-driver to be installed."
),
"parameters": {
"type": "object",
"properties": {
"action": {
"type": "string",
"enum": [
"capture",
"click",
"double_click",
"right_click",
"middle_click",
"drag",
"scroll",
"type",
"key",
"set_value",
"wait",
"list_apps",
"focus_app",
],
"description": (
"Which action to perform. `capture` is free (no side "
"effects). All other actions require approval unless "
"auto-approved. Use `set_value` for select/popup elements "
"and sliders — it selects the matching option directly "
"without opening the native menu (no focus steal)."
),
},
# ── capture ────────────────────────────────────────────
"mode": {
"type": "string",
"enum": ["som", "vision", "ax"],
"description": (
"Capture mode. `som` (default) is a screenshot with "
"numbered overlays on every interactable element plus "
"the AX tree — best for vision models, lets you click "
"by element index. `vision` is a plain screenshot. "
"`ax` is the accessibility tree only (no image; useful "
"for text-only models)."
),
},
"app": {
"type": "string",
"description": (
"Optional. Limit capture/action to a specific app "
"(by name, e.g. 'Safari', or bundle ID, "
"'com.apple.Safari'). If omitted, operates on the "
"frontmost app's window or the whole screen."
),
},
"max_elements": {
"type": "integer",
"description": (
"Optional cap on the AX `elements` array returned by "
"`action='capture'`. Default 100, hard maximum 1000. "
"Dense UIs (Electron apps such as Obsidian or VS Code, "
"JetBrains IDEs) can publish 500+ AX nodes — capping "
"prevents a single capture from blowing session "
"context. When the cap trims the response, "
"`total_elements` and `truncated_elements` are "
"surfaced in the result so you can re-call with "
"`app=` to narrow scope or raise `max_elements` when "
"the full tree is required. Has no effect on "
"`mode='som'` / `mode='vision'` when a screenshot is "
"included in the response; only the rare image-"
"missing fallback returns an `elements` array and is "
"subject to the cap."
),
"default": 100,
"minimum": 1,
"maximum": 1000,
},
# ── click / drag / scroll targeting ────────────────────
"element": {
"type": "integer",
"description": (
"The 1-based SOM index returned by the last "
"`capture(mode='som')` call. Strongly preferred over "
"raw coordinates."
),
},
"coordinate": {
"type": "array",
"items": {"type": "integer"},
"minItems": 2,
"maxItems": 2,
"description": (
"Pixel coordinates [x, y] in logical screen space (as "
"returned by capture width/height). Only use this if "
"no element index is available."
),
},
"button": {
"type": "string",
"enum": ["left", "right", "middle"],
"description": "Mouse button. Defaults to left.",
},
"modifiers": {
"type": "array",
"items": {
"type": "string",
"enum": ["cmd", "shift", "option", "alt", "ctrl", "fn"],
},
"description": "Modifier keys held during the action.",
},
# ── drag ───────────────────────────────────────────────
"from_element": {"type": "integer",
"description": "Source element index (drag)."},
"to_element": {"type": "integer",
"description": "Target element index (drag)."},
"from_coordinate": {
"type": "array",
"items": {"type": "integer"},
"minItems": 2, "maxItems": 2,
"description": "Source [x,y] (drag; use when no element available).",
},
"to_coordinate": {
"type": "array",
"items": {"type": "integer"},
"minItems": 2, "maxItems": 2,
"description": "Target [x,y] (drag; use when no element available).",
},
# ── scroll ─────────────────────────────────────────────
"direction": {
"type": "string",
"enum": ["up", "down", "left", "right"],
"description": "Scroll direction.",
},
"amount": {
"type": "integer",
"description": "Scroll wheel ticks. Default 3.",
},
# ── set_value ──────────────────────────────────────────
"value": {
"type": "string",
"description": (
"For action='set_value': the value to set on the element. "
"For AXPopUpButton / select dropdowns, pass the option's "
"display label (e.g. 'Blue'). For sliders and other "
"AXValue-settable elements, pass the numeric or string value."
),
},
# ── type / key / wait ──────────────────────────────────
"text": {
"type": "string",
"description": "Text to type (respects the current layout).",
},
"keys": {
"type": "string",
"description": (
"Key combo, e.g. 'cmd+s', 'ctrl+alt+t', 'return', "
"'escape', 'tab'. Use '+' to combine."
),
},
"seconds": {
"type": "number",
"description": "Seconds to wait. Max 30.",
},
# ── focus_app ──────────────────────────────────────────
"raise_window": {
"type": "boolean",
"description": (
"Only for action='focus_app'. If true, brings the "
"window to front (DISRUPTS the user). Default false "
"— input is routed to the app without raising, "
"matching the background co-work model."
),
},
# ── return shape ───────────────────────────────────────
"capture_after": {
"type": "boolean",
"description": (
"If true, take a follow-up capture after the action "
"and include it in the response. Saves a round-trip "
"when you need to verify an action's effect."
),
},
},
"required": ["action"],
},
}
def get_computer_use_schema() -> Dict[str, Any]:
"""Return the generic OpenAI function-calling schema."""
return COMPUTER_USE_SCHEMA