Why Actions are the hard part
Instructions and files are text. Actions are working connections: a schema, a server URL and authentication. OpenAI's migration guide states that custom actions do not transfer and must be rebuilt separately, using a supported app or a custom MCP server.
Step 1: Inventory
For each Action write down: the endpoint and method, what it returns, the server URL, the authentication type, and which line of your instructions tells the GPT when to call it. The free checker lists endpoints, servers and auth from a pasted OpenAPI schema.
Step 2: Decide how to reconnect
- A supported app: if the service you call already has one, connect that.
- A custom MCP server: OpenAI describes MCP servers as the way a plugin exposes tools with input and output schemas and authentication.
- Drop it: if the Action is rarely used, a manual step may be enough.
Step 3: Re-authorize and test
OAuth connections usually need to be authorized again. Test each call end to end, including error cases.
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