cad-urdf-skill

cad-urdf-skill is a skill for OpenCode from darellchua2/opencode-config-template. It costs 56 tokens per session (1,162 once invoked), scanned A, original, Apache-2.0.

A generator and validator for URDF robot descriptions, which are files that define a robot’s links, joints, shapes, limits, and physical properties.

In plain words
What is it for?
Use it to create and validate URDF files from genurdf() sources while keeping the source code as the authoritative definition.
Why use it?
It helps catch mistakes in robot frames, joint axes, units, mesh scale, and inertial data before the description is used elsewhere.

Skill for OpenCode

Written for OpenCode: installed under .opencode/. Also seen: mentions OpenCode.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/darellchua2/opencode-config-template/cad-urdf-skill
Any agent
npx skills add darellchua2/opencode-config-template --skill cad-urdf-skill
Clone the repo
git clone --depth 1 https://github.com/darellchua2/opencode-config-template

Made for: OpenCode.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for cad-urdf-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/darellchua2/opencode-config-template/cad-urdf-skill.svg)](https://agentmods.dev/skills/darellchua2/opencode-config-template/cad-urdf-skill)
Your own site
<a href="https://agentmods.dev/skills/darellchua2/opencode-config-template/cad-urdf-skill"><img src="https://agentmods.dev/badge/skills/darellchua2/opencode-config-template/cad-urdf-skill.svg" alt="Measured on agentmods" height="20"></a>
Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,162 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00056 $0.01162
Opus 5 $0.00028 $0.00581
Sonnet 5 $0.00011 $0.00232
Haiku 4.5 $0.00006 $0.00116

Measured 2d ago against content hash cf2fbb67ba42, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

cad-urdf-skill scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 6 executable files (scripts/packages/cadpy_metadata/src/cadpy_metadata/__init__.py, scripts/packages/cadpy_metadata/src/cadpy_metadata/generator.py, scripts/urdf/__init__.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

opencode_app/.opencode/skills/cad-urdf-skill/SKILL.md · 73 lines

How it starts

The opening of the file, as written. The whole thing — 73 lines — stays where its author put it; the contents beside it link to each section on GitHub.

URDF

Provenance: maintained in earthtojake/text-to-cad. Use the installed local skill files as the runtime source of truth; the repository link is only for provenance and release review.

Use this skill for URDF robot-description outputs. Treat URDF work as constrained kinematic modeling, not just XML writing. The main correctness risks are frame placement, joint-axis semantics, unit consistency, mesh scale, inertial data, and generated-artifact drift.

Core Rules

  1. Treat the Python source that defines gen_urdf() as the source of truth. Treat configured .urdf files as generated artifacts.
  2. Generate only explicit URDF targets. Do not regenerate unrelated CAD, mesh, render, SRDF, SDF, or simulator artifacts from this skill.
  3. The scripts/urdf generator validates generated URDFs by default. Do not use or document a separate validate command.
  4. Before writing or changing URDF XML, establish the robot's frame, joint, geometry, unit, and assumption ledger. See references/design-ledger.md.
  5. Use URDF frame semantics exactly. Joint origins, link frames, joint axes, and visual/collision/inertial origins use different reference frames. See references/frame-semantics.md.
  6. Do not infer spatial transforms, mesh units, handedness, axes, or joint signs from vague prose. Use CAD transforms, dimensioned drawings, measured values, existing source data, or explicit documented assumptions.
  7. Prefer simple, auditable generator code over clever XML construction. Keep constants named by physical meaning, not by arbitrary numbers.
  8. For physical links, model inertial, visual, and collision separately when the target consumer needs them. Frame-only links may intentionally omit mass and geometry.

CAD Viewer Handoff

After completing URDF work that creates or modifies a .urdf, you must ALWAYS hand the explicit file path to the cad-viewer-skill (load via skill tool) when that skill is installed. the cad-viewer-skill (load via skill tool) must start CAD Viewer if it is not already running and return link(s) to the relevant created or updated file(s); if the cad-viewer-skill (load via skill tool) is unavailable or startup fails, report that instead of silently omitting the handoff.

Read the full file on GitHub · 73 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 73 lines · 56 tokens per session scan A cf2fbb67ba42

Subscribe to this mod's changes

cad-urdf-skill is a skill published in the GitHub repository darellchua2/opencode-config-template (6 stars, last pushed 5d ago), licensed Apache-2.0. It adds 56 tokens to every session and 1,162 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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