Convert URDF to MuJoCo MJCF Without Installing Anything API + Python SDK

Source: Dev.to

The Problem

• MuJoCo is the fastest‑growing robotics simulator.
• Converting URDF to MJCF is painful: the ./compile tool is buggy, urdf2mjcf ignores off‑diagonal inertia, and mesh paths often break.
• You just want to convert and start training your RL agent.

The Solution

Curl

curl -X POST https://api.example.com/api/urdf/convert-format?target=mjcf \
  -H "X-Api-Key: rk_..." \
  -F "file=@robot.urdf"

Python SDK

import roboinfra

client = roboinfra.Client("rk_...")
result = client.urdf.convert_format("robot.urdf", "mjcf")

with open("robot.xml", "w") as f:
    f.write(result.converted_xml)

Real Example (preview_test_arm.urdf)

• Input URDF – a robot with 6 links and 5 joints.
• Output MJCF – includes actuators, floor, and lighting.

This conversion would take 2–3 hours manually; the API completes it in ~200 ms.

Also Converts to Gazebo SDF

The same API can produce an SDF file; just change the target parameter:

curl -X POST https://api.example.com/api/urdf/convert-format?target=sdf \
  -H "X-Api-Key: rk_..." \
  -F "file=@robot.urdf"

The returned SDF output contains the equivalent Gazebo description.

Bonus: Validate + Convert in CI

Add a short GitHub Action to validate the URDF and convert it to MJCF on every push:

name: URDF Validation & Conversion
on: [push]

jobs:
  convert:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Convert URDF to MJCF
        run: |
          curl -X POST https://api.example.com/api/urdf/convert-format?target=mjcf \
            -H "X-Api-Key: ${{ secrets.ROBOINFRA_API_KEY }}" \
            -F "file=@path/to/robot.urdf"

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