Can ChatGPT connect to any MCP server?

To third-party remote MCP servers, yes — through custom connectors with developer mode enabled. Without developer mode, connectors are restricted to search and fetch, which is enough to read but not to act.

Which ChatGPT plans support custom MCP connectors?

Business, Enterprise and Edu accounts have the full MCP surface. OpenAI’s documentation has been inconsistent about the consumer tiers, so the reliable test is whether the developer mode toggle appears in your own settings.

Do I need an API key?

No. ChatGPT’s connector flow is built around OAuth, and FishOut speaks it, so you sign in and approve rather than paste anything.

Does agent mode use my FishOut connector?

No. Agent mode does not use custom apps, so a delegated task will not call FishOut. Use it directly in a conversation with an @mention instead.

MCP · Hosted chat

Connect FishOut to ChatGPT (MCP setup)

ChatGPT can connect to third-party MCP servers, but not from the default interface — the full tool surface lives behind developer mode, and which plans get it is the part people get wrong.

Start free Read the MCP docs

Setup steps checked against ChatGPT's own documentation on 20 October 2026.

[01] CONNECT IT/ SETUP

Add FishOut to ChatGPT

https://mcp.fishout.ai/mcp, on every plan.

Turn on developer mode

Open ChatGPT Settings and look for developer mode. Depending on your account it sits under Security and login, or under Apps → Advanced settings. Turning it on is what exposes the full MCP surface — including write tools — rather than the search-and-fetch subset.

Add FishOut as a connector

From the connectors or apps list, create a new connector and paste the server URL. Give it a name and a short description so it is recognisable in the composer.

server url

https://mcp.fishout.ai/mcp

Choose OAuth as the authentication method and connect. ChatGPT sends you to FishOut: sign in, pick the organization and projects, and approve. A chat client is where a read-only grant earns its keep.

Scan the tools and use it

Use the Scan Tools action to have ChatGPT enumerate what FishOut exposes, then @mention the connector in a message to bring it into a conversation.

Check it worked. Run Scan Tools on the connector and check that the FishOut tools are listed, then @mention it in a new chat and ask a read-only question before enabling anything that writes.

[02] WORTH KNOWING FIRST/ LIMITS

Before it bites

Stated before you hit them.

Developer mode is what unlocks full MCP. Without it, connectors are limited to search and fetch, which rules out adding keywords, replying or assigning.

Plan availability differs by tier and OpenAI’s own documentation is not consistent about which consumer plans qualify — check the setting in your account rather than trusting a table.

Custom connectors are a web feature. The ChatGPT mobile apps will not see them.

FishOut is not in the ChatGPT app directory, so it is added as a custom connector. In our 19 October run ChatGPT connected and signed in; we have not yet recorded tool calls from it.

[03] WHAT IT LOOKS LIKE/ CHATGPT

A question in ChatGPT

Invented brands; a real call.

ChatGPT · developer modefishout · mcp

@FishOut which posts in the Leads view should I answer first, and why?

list_mentionsread-onlyarguments

{
  "filter": {
    "view": "leads",
    "sort": "best"
  },
  "limit": 5
}

r/SaaSnorthfold2h

Looking for a shared inbox that two founders can actually split

Reply nowAsking for recommendations

Hacker Newsquietcartographer1d

Compared three inbox tools for a support team of four

Reply, carefullyComparison

Answer r/SaaS first: two hours old, asking exactly what you do, no vendor replies yet. The HN comparison is a day old and already has replies — only join if you can add a number they do not have.

[04] WATCH ANY PLATFORM/ SAME SERVER