urdf

urdf is a skill for Claude Code, Codex from earthtojake/text-to-cad. It costs 92 tokens per session (1,741 once invoked), scanned A, original, MIT.

Guidance for writing and checking URDF files, XML descriptions that define a robot's links, joints, shapes, limits, and physical properties. It focuses on how robot parts are positioned and connected.

In plain words
What is it for?
Use it when creating or debugging robot descriptions, including links, joints, visual and collision geometry, mesh references, limits, and inertial properties.
Why use it?
It helps prevent errors in coordinate frames, joint axes, units, mesh scale, and inertial data that can make a robot model behave incorrectly. It also keeps assumptions explicit in the source file.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present. Also seen: $skill-name invocation.

Part of the cad plugin — 12 skills shipped together

Good fit Use it when creating or debugging robot descriptions, including links, joints, visual and collision geometry, mesh references, limits, and inertial properties.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/earthtojake/text-to-cad/urdf
About the project

text-to-cad is a collection of agent workflows for creating, examining, finding, preparing, and transferring CAD, engineering, manufacturing, and robot-description files. It is for agents working with mechanical design, fabrication, simulation, and robotics projects. Catalogue skills, instructions, and a plugin implement these workflows.

earthtojake/text-to-cad · 14,805 stars · on GitHub · texttocad.dev

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.

Any agent
npx skills add earthtojake/text-to-cad --skill urdf
Clone the repo
git clone --depth 1 https://github.com/earthtojake/text-to-cad

Made for: Claude Code, Codex.

Or install cad, the plugin that ships this one along with the rest of its 12 skills.

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 urdf

README.md
[![agentmods](https://agentmods.dev/badge/skills/earthtojake/text-to-cad/urdf/github.svg)](https://agentmods.dev/skills/earthtojake/text-to-cad/urdf)
Your own site
<a href="https://agentmods.dev/skills/earthtojake/text-to-cad/urdf"><img src="https://agentmods.dev/badge/skills/earthtojake/text-to-cad/urdf/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for urdf

Your own site · 80×15
<a href="https://agentmods.dev/skills/earthtojake/text-to-cad/urdf"><img src="https://agentmods.dev/badge/skills/earthtojake/text-to-cad/urdf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 92 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,741 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Socket pass 13 May 2026
  • Snyk pass 13 May 2026
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00092 $0.01741
Opus 5 $0.00046 $0.00870
Sonnet 5 $0.00018 $0.00348
Haiku 4.5 $0.00009 $0.00174

Measured 5d ago against content hash b3531395bd93, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

urdf 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 5d ago.

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.

skills/urdf/SKILL.md · 111 lines

How it starts

The opening of the file, as written. The whole thing — 111 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, and inertial data.

Setup

This skill's commands are thin entrypoints over the cadgen distribution, which carries the Python build runtime and the JavaScript it executes. Install it once:

python -m pip install -r requirements.txt

Rendering additionally needs a browser, which pip cannot supply:

python -m playwright install chromium

Core Rules

  1. The .urdf file is the source of truth. Author and edit URDF XML directly; do not build a Python generation pipeline for it. There is no gen_urdf() contract.
  2. Before writing or changing URDF XML, establish the robot's frame, joint, geometry, unit, and assumption ledger and embed it as a comment block at the top of the .urdf file. See references/design-ledger.md.
  3. 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.
  4. 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.
  5. Never freehand numeric values that are the result of computation — inertia tensors, centers of mass, unit conversions across many links, mirrored transforms. Compute them: closed-form formulas for primitives, or a throwaway helper script for mesh-derived values. See references/inertials.md.
  6. For physical links, model inertial, visual, and collision separately when the target consumer needs them. Frame-only links may intentionally omit mass and geometry.
  7. Validate every created or modified .urdf with cadgen urdf validate before reporting completion. See references/validation.md.
  8. Helper scripts are allowed and encouraged for computation, but they are scaffolding, not the artifact's source of truth. For complex or genuinely parametric models it is reasonable to keep a model-local helper script on disk next to related source code (for example STEP generator sources) and note it in the ledger; this is optional, and the checked-in .urdf remains canonical.

Read the full file on GitHub · 111 lines

Files

What ships with it

10 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 5d ago Changed · +18 lines · -14 tokens per session b3531395bd93
  2. 10d ago First seen · 93 lines · 106 tokens per session scan A a2d701e8140d

Subscribe to this mod's changes

urdf is a skill published in the GitHub repository earthtojake/text-to-cad (14,805 stars, last pushed yesterday), licensed MIT. It adds 92 tokens to every session and 1,741 once invoked, about $0.0005 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 2026-08-30.

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