/srdf

name: srdf
description: MoveIt2 SRDF authoring, validation, and planning-semantics workflow. Use when creating, editing, inspecting, or validating `.srdf` files, MoveIt planning groups, virtual joints, passive joints, end effectors, group states, disabled collisions, URDF-paired planning semantics, or SRDF handoff for live review. Use the URDF skill for robot structure, the SDF skill for simulator descriptions, and the cad-viewer skill for rendering and live review links.

SRDF

Provenance: maintained in [earthtojake/text-to-cad](https://github.com/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 MoveIt semantic robot descriptions on top of an existing valid URDF. SRDF defines planning semantics; it does not define physical robot structure. The `.srdf` file is the source of truth: author and edit the XML directly. There is no `gen_srdf()` contract.

SRDF correctness is a **planning semantics** problem. The common failure is not invalid XML; it is a plausible SRDF that gives MoveIt the wrong planning group, wrong tool link, wrong default state, unsafe disabled-collision matrix, or wrong joint units. Because language models are weak at spatial and kinematic reasoning, derive planning groups, end effectors, group states, and disabled collisions from the URDF topology, MoveIt Setup Assistant output, sampled collision analysis, or explicit user data. Do not infer them from visual theme alone — and do not type any link or joint name from memory: extract the URDF's link/joint table first and copy names from it.

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

Format boundary

• **URDF** owns physical robot structure: links, joints, geometry, inertials, limits, mimic joints, transmissions, and robot-state publishing.
• **SRDF** owns MoveIt semantics: virtual joints, passive joints, planning groups, group states, end effectors, and disabled collision pairs.
• **SDF** owns simulator/world semantics: physics, sensors, lights, plugins, worlds, and simulation-specific metadata.

Do not place geometry, inertials, joint origins, link poses, mesh references, physical joint limits, transmissions, or `ros2_control` interfaces in SRDF.

CAD Viewer Handoff

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

Required workflow

1. **Start from a valid URDF.** Author or fix the URDF first with `$urdf` and validate it. The SRDF pairs with that URDF by colocation and robot name, and every name in the SRDF must exist in it. 2. **Extract the URDF table.** Before writing any SRDF XML, list the URDF's robot name, links, joints (with type, parent, child, limits, mimic flags). Copy names from this table only; never type them from memory. See `references/srdf-workflow.md`. 3. **Identify the planning task.** Record whether the goal is arm IK, gripper control, mobile base planning, dual-arm planning, tool use, or local smoke testing. 4. **Create or update the planning ledger.** Use `references/planning-ledger.md` before writing XML; keep a compact copy as a comment block in the `.srdf`. 5. **Pair with the URDF by colocation.** Save the `.srdf` in the same folder as its `.urdf`, with the same `<robot name>` — that is the only linking mechanism. The validator and the viewer both resolve the pairing by scanning the folder for the URDF whose robot name matches; exactly one URDF per robot name per folder. No metadata element links the files. See `references/authoring-contract.md`. 6. **Define virtual and passive joints deliberately.** Use them when needed by the robot model. 7. **Define planning groups from URDF topology.** Prefer chain groups for serial manipulators when base/tip form a real parent-to-child path in the URDF tree (the validator verifies this). Use joint/link/subgroup definitions only when they are deliberate. 8. **Define end effectors after group membership is known.** Avoid overlap between an end-effector group and its parent group. Record the actual target/TCP link. 9. **Define group states in URDF-native units.** Revolute and continuous values are radians; prismatic values are meters. Do not store degrees in SRDF. Values must lie within URDF limits and must not set fixed or mimic joints. 10. **Generate disabled collisions from evidence.** Use adjacency derived from the URDF joint table, MoveIt Setup Assistant sampling, or explicit user-provided collision matrices. Do not invent broad disable lists. See `references/disabled-collisions.md`. 11. **Validate every created or modified `.srdf`** with `cadgen srdf validate`; it cross-validates all names, chains, states, and pairs against the paired URDF. Fix findings and re-validate until clean. 12. **Run MoveIt smoke tests when available.** Use MoveIt Setup Assistant or a project MoveIt launch directly. 13. **Report assumptions and skipped checks.** Include incomplete validation, missing MoveIt environment, manually reasoned collision disables, and inferred target links.

Commands

Run with the Python environment for the project or workspace. Treat `python` in examples as an interpreter placeholder; if bare `python` is unavailable, substitute `python3`, a project virtualenv interpreter, or the configured interpreter path. The validator uses only the Python standard library.

The validator shape