Custom GPT to Plugin Migration Guide

A · Use the built-in “Migrate to plugin” option

1. Finish and publish your edits. In the GPT builder, review instructions and knowledge files, then publish the latest version. It does not have to be shared publicly.
2. Start the conversion. Open My GPTs → Created by me, select the GPT, and choose Migrate to plugin. Follow the on-screen review and creation steps.
3. Review the result. Check the new skill instructions, copied knowledge/reference files, and connected apps. The selected model and Custom Actions do not transfer; rebuild any required Action separately.
4. Install and test privately. Find the plugin under Customize → Plugins where available, install it if prompted, then test familiar and difficult tasks in a new conversation.
5. Share after validation. Give intended users access and ask one colleague to install and try it. Existing GPT sharing permissions do not carry over.

If you cannot see the migration option, check the account/workspace where the GPT was created, that it is published, and that plugins are enabled; availability can vary.

B · Create the plugin files and folders manually

Example: turn an “SEO Content Brief” GPT into a plugin containing one skill. This path uses a local folder and a portable plugin manifest. You can edit the files in any plain-text editor.

1. Create the folder structure shown below. Copy any approved brand guide and brief template into references/. Create another folder under skills/ for each distinct workflow.
2. Write plugin.json. Place it at the root of the plugin folder; use a stable lowercase name with hyphens.
3. Write SKILL.md. Give it YAML frontmatter with name and description. In the body, adapt the GPT's purpose, trigger, required inputs, steps, output format, and missing-information rules. Point to each reference file by its relative path.
4. Handle integrations separately. A skill can describe when to use an available app, but text alone does not connect it. Configure an approved app or MCP connection and test its permissions. A GPT Custom Action requires its own replacement.
5. Add the local plugin to a marketplace and install it. Ask @plugin-creator to register this existing folder in a personal marketplace, or follow the manual marketplace instructions. Restart the desktop app if necessary, find the plugin in the Plugins Directory, install it, and test it in a new chat. Local marketplace distribution and workspace-wide sharing are separate steps.

seo-content-plugin/
  plugin.json
  skills/
    seo-content-brief/
      SKILL.md
      references/
        brief-template.md
        brand-voice.md

{
  "$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json",
  "name": "seo-content-plugin",
  "version": "1.0.0",
  "description": "Reusable SEO content brief workflow"
}

---
name: seo-content-brief
description: Create an SEO content brief from a keyword, audience, and source material. Use when a user asks for a brief; do not publish content.
---

# SEO content brief

1. Ask for the target keyword, audience, and page goal if missing.
2. Review references/brief-template.md and references/brand-voice.md.
3. Draft search intent, outline, questions to answer, and CTA guidance.
4. Use the template headings. Flag unsupported claims for review.
5. Return a draft for a human editor to check before use.

The portable manifest discovers skills in the root skills/ folder. These example reference files are placeholders: copy in your real approved files. If Plugin Creator scaffolds .codex-plugin/plugin.json instead, that is a supported compatibility layout; follow the file paths it generates rather than mixing the two layouts.

C · Use AI to repackage the GPT

Use this path when you want help turning existing instructions and files into a clean plugin. You still need to supply the GPT configuration and original knowledge files. AI cannot infer what is in a file it has not been given.

1. Gather the inputs. Copy the GPT's published instructions into a text file. Download or locate the original knowledge documents. Save example outputs and test prompts, plus a list of apps and Custom Actions.
2. Start Plugin Creator. In ChatGPT Chat or Work, type @ and select Plugin Creator if your workspace offers it. For a local development workflow in Codex, use the available @plugin-creator or $plugin-creator skill as shown in your environment.
3. Attach the source material and paste the brief below. Ask it to separate stable workflow instructions from supporting references, to show the proposed structure, and to flag integrations it cannot transfer.
4. Inspect the draft. Confirm the skill description triggers for the right request, the full instructions preserve critical rules, reference files are included, and any dependencies are actually configured. Revise with follow-up prompts.
5. Finish, install, and test. Follow Plugin Creator's prompts to create the plugin, install it if prompted, and compare the results with your saved GPT examples. Share only after another intended user can use it.

Create a private plugin to replace my existing "SEO Content Brief" Custom GPT.
I am attaching its published instructions, original knowledge files,
one example output, and several test prompts.

Please:
1. Make a reusable skill for creating SEO content briefs.
2. Put the lasting process, inputs, output format, and review rules in
   the skill instructions. Keep the approved brief template and brand
   voice guide as reference files.
3. Show me the proposed skill name, description, file structure,
   and a list of what was copied, rewritten, or omitted.
4. List every connected app and Custom Action separately. Do not
   claim an integration is working until it has been connected and tested.
5. Ask me about any missing source file or unclear instruction.
6. Keep it private while we run the attached test prompts.

Do not invent facts, brand guidance, or permissions that are absent
from the source materials.

For a manual file package assisted by AI, replace the first line with: “Create a local, portable plugin folder with a root plugin.json, skills/<name>/SKILL.md, and the original supporting files in references/. Show me the files before any installation.” Have a person review the generated files before they are installed.