How to add a custom connector in ChatGPT, step by step.
ChatGPT can connect to outside tools through custom connectors. Here is exactly how to set one up, with FoxEra's calling server as the worked example so you can test it straight away.
What is a custom connector in ChatGPT?
A custom connector lets ChatGPT talk to an outside service. Instead of being limited to what ChatGPT knows from training, you give it a live link to a tool it can read from and write to. OpenAI calls this feature Developer mode, and the connection itself is sometimes called an MCP server or a connected data source.
Once connected, you can ask ChatGPT questions that the tool can answer — for example, "how many leads are in my campaign?" or "what did the last batch of calls cost?" The connector handles the request behind the scenes and returns the answer into your chat.
Before you start
You need three things:
- A ChatGPT account on the Plus, Team or Enterprise plan. Custom connectors are not available on the free plan at the time of writing.
- The MCP server URL for the tool you want to connect. For FoxEra Calls, the URL is https://app.foxera.co.uk/mcp.
- An account on the tool itself. If you are using FoxEra as the example, sign up at foxera.co.uk first — new accounts get £7 of free calling credit.
If you want to understand what an MCP server actually is before connecting one, read the developer guide for a plain-English explanation.
Step-by-step: adding the connector
Open ChatGPT and follow these steps:
- Open Settings. Click your profile icon in the bottom-left corner, then choose Settings.
- Find Developer mode. In the sidebar, look for a section called Developer or Connected data. Turn Developer mode on if it is not already enabled.
- Create a new connector. Click Add connector (or Create connector). You will see a field for the server URL.
- Paste the MCP URL. Enter https://app.foxera.co.uk/mcp and click Connect.
- Authorise the connection. ChatGPT will open an OAuth prompt asking you to allow the connector to access your FoxEra account. Review the permissions and click Allow.
- Test it. Go back to a new chat and ask something like "check my account status" or "list my campaigns". ChatGPT should call the connector and return a live answer.
The whole process takes under two minutes. If the OAuth prompt does not appear, check that you are logged into FoxEra in the same browser.
What you can do once connected
With the FoxEra connector active, ChatGPT can:
- Add leads — paste a list of businesses and ask ChatGPT to upload them to a campaign folder.
- Preview a campaign — ask how many leads are queued, which AI agent will call, and what the estimated cost is.
- Start a campaign — after you approve, ChatGPT sends the instruction to begin calling. Nobody is phoned without your explicit approval.
- Read outcomes — ask who answered, who asked for a callback, and what each call cost. ChatGPT can read the full transcripts and summarise them for you.
The same connector works for any MCP-compatible tool, not just FoxEra. The steps are identical — only the URL changes.
Troubleshooting common problems
If the connector does not work on the first try, check these things:
- Developer mode is off. Go back to Settings and confirm the toggle is on. ChatGPT sometimes resets it after updates.
- Wrong URL. Make sure the URL is exactly https://app.foxera.co.uk/mcp with no trailing spaces or extra characters.
- OAuth not completed. If you closed the authorisation window before clicking Allow, delete the connector and add it again.
- Free-plan account. Custom connectors require a paid ChatGPT plan. If you are on the free tier, you will not see the Developer mode option.
If you prefer to use Claude, Cursor or another assistant instead of ChatGPT, the process is similar. See how to connect ChatGPT to cold calling or the full developer guide for other assistants.
Frequently asked questions
Is adding a custom connector in ChatGPT free?
The connector feature itself is included in ChatGPT Plus, Team and Enterprise plans. The tool you connect may have its own pricing. FoxEra Calls charges from 12p per connected minute with no subscription, and new accounts start with £7 of free calling credit.
Can ChatGPT make phone calls through a custom connector?
Yes, if the connected tool supports it. With FoxEra's connector, ChatGPT can set up and run a calling campaign on your behalf. Every campaign still needs your explicit approval before anyone is phoned.
Will the connector share my data with OpenAI?
The connector sends requests to the tool's server, not to OpenAI's training pipeline. Your calling data stays on FoxEra's servers. Check OpenAI's data-use policy for how chat content is handled on their side.