# Proposing Short Axis Grasps

> Propose top-down grasps whose jaws close ACROSS an elongated object's short axis, derived from its oriented box. Use when the object is longer than it is wide, as the first grasp-proposal rung — a handle, a spanner, a screwdriver, a bar, a laid-down bottle — where closing along the length would put the fingers down the object and meet them on each other. Declines when the short axis is wider than the hand opens, which is the signal to try `proposing-side-grasps` rather than to re-tune this one.

- Skill: `graph-robots/proposing-short-axis-grasps` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add graph-robots/proposing-short-axis-grasps`
- Raw SKILL.md: https://api.skillmd.com/api/skills/graph-robots/proposing-short-axis-grasps/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: graph-robots (https://skillmd.com/u/graph-robots)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/graph-robots/proposing-short-axis-grasps

---


# proposing-short-axis-grasps

One strategy for the **propose** stage of a pick: a top-down grasp across the
narrow dimension of an elongated body.

## Why this is its own skill

A pick has stages — propose, select, approach, close — and each has more than
one strategy. Treating "grasping" as one indivisible thing is what leaves a
policy with a single approach and nowhere to go when it does not fit: it can
only jitter the numbers of a strategy that structurally cannot work. Proposing
is separated from selecting so that a refusal here (*"the short axis is wider
than the hand"*) is a **routable exit** to a different rung, not a failed
episode.

## When to use

- The target is longer than it is wide: a handle, spanner, screwdriver, bar.
- Top-down access is available.
- Any privilege tier. The box may come from `sim.get_object_obb` **or** from
  `geometry.compute_obb` over a segmented cloud — this skill cannot tell which,
  which is what makes it portable to the vision body.

## When NOT to use

- The top is blocked (a shelf, a lid) — use `proposing-side-grasps`.
- The body is roughly cubic; there is no meaningful short axis to close across.
- The graspable part is a concave interior (the inside of a ring, a pivot
  between two plates). A box has no opinion about concavity, and neither has
  this skill.

## Recommended subgraph state flow

```text
describe → get_obb → propose → frame → select → END
```

1. **`describe`** — `tool: robot.describe_gripper` (for the jaw span).
2. **`get_obb`** — `tool: sim.get_object_obb`, `inputs: {object_name: …}`.
   At `camera_only`/`none`, substitute `geometry.filter_and_compute_obb`.
3. **`propose`** — `script: scripts/<sg>/propose_short_axis.py`, inputs
   `target_obb = Ref("get_obb.obb")`, `gripper = Ref("describe")`.
   Router on `route`: `proposed` → `frame`, `declined` → the subgraph's
   `declined` exit.
4. **`frame`** — `tool: robot.grasp_frame`, `inputs:
   {close_heading_deg: Ref("propose.close_heading_deg")}`.
5. **`select`** — hand `propose.positions` and `frame.rotation` to
   `selecting-reachable-grasp`, which walks them.

## Required end states

| End state | Meaning |
|---|---|
| `proposed` | A heading and stations. Continue to select. |
| `declined` | The hand cannot span this object's short axis. Route to another propose rung — do not retry this one with different numbers. |