Simon Willison’s Weblog

Skills in OpenAI API. OpenAI's adoption of Skills continues to gain ground. You can now use Skills directly in the OpenAI API with their shell tool. You can zip skills up and upload them first, but I think an even neater interface is the ability to send skills with the JSON request as inline base64-encoded zip data, as seen in this script:

r = OpenAI().responses.create(
    model="gpt-5.2",
    tools=[
      {
        "type": "shell",
        "environment": {
          "type": "container_auto",
          "skills": [
            {
              "type": "inline",
              "name": "wc",
              "description": "Count words in a file.",
              "source": {
                "type": "base64",
                "media_type": "application/zip",
                "data": b64_encoded_zip_file,
              },
            }
          ],
        },
      }
    ],
    input="Use the wc skill to count words in its own SKILL.md file.",
)
print(r.output_text)

I built that example script after first having Claude Code for web use Showboat to explore the API for me and create this report. My opening prompt for the research project was:

Run uvx showboat --help - you will use this tool later

Fetch https://developers.openai.com/cookbook/examples/skills_in_api.md to /tmp with curl, then read it

Use the OpenAI API key you have in your environment variables

Use showboat to build up a detailed demo of this, replaying the examples from the documents and then trying some experiments of your own