How it works on Claude and on OpenAI

If you will not build a product, skip this section and go on to "Where the book teaches this".

The same server works on both platforms, because both connect to outside tools through MCP, the Model Context Protocol: one standard plug for AI apps. Build your server to it once, and any AI app that supports MCP can plug in. Both platforms also support MCP Apps, MCP's shared way for a server to show its own screens inside the chat.¹ What differs is how customers find the product, see it and pay for it. Each vendor sets these rules and changes them often, so this section is checked every month. Check them again before you sell.

On Claude

As of October 29, 2026, connectors work like this:

• For everyone, you can list your connector in Anthropic's connector directory, from any paid Claude plan. Anthropic checks it against its directory policy, which does not admit connectors that serve ads, or that move money without a person approving.⁴,⁵
• A connector that is not listed can still be shared with an install link.⁶
• On the free plan, a customer can use connectors from the directory and add one custom connector. Plugins need a paid plan.⁷,⁸,⁹
• A connector can show its own screens inside the chat, on every plan.¹⁰

Artifacts that use Claude are shared like this:¹¹

• An Artifact that uses Claude or connected apps cannot be shared with "anyone with the link", on any plan.
• Inside a Team or Enterprise organization, you can share it with specific people or the whole organization, and on Enterprise with groups. Each person uses their own plan and their own connections.¹²
• People outside the organization can be invited by email, a feature in beta, and can open it, but Claude and connectors do not work for them. On Team and Enterprise, an owner must first allow invitations outside the organization.
• On Pro, Max and Ultra, only people you invite by email can open it, as of October 31, 2026.¹³ The help page says the parts that use Claude or connectors do not work for people invited from outside your organization, but not what that means on a personal plan. Test this before you sell to individuals this way.
• Legacy Artifacts, made in a chat before September 16, 2026, follow older rules.¹²

So today, an Artifact that calls Claude works fully for customers inside an organization. A connector reaches individuals too, on every plan, and it can bring its own screens.

On OpenAI

Building it. You build an app for ChatGPT with OpenAI's Apps SDK. The app is your MCP server plus, if you want one, an interface that ChatGPT shows inside the chat, such as interactive cards.¹⁴ So on OpenAI, the conversation and the guided screens can live in one app. As on Claude, an app can also go in a plugin, which brings apps and skills together.¹⁵

Signing in. Your server signs users in with OAuth 2.1, following the MCP authorization standard. ChatGPT sends a token with every call, and your server checks it before running any tool. If the check fails, your server returns an error that makes ChatGPT ask the user to sign in again.¹⁶ This is where your check of who has paid belongs.

Who pays. Using an app may count toward the user's ChatGPT plan limits, and toward limits the app's maker sets.¹⁷ As on Claude, any model your own server calls is billed to you.

Reaching customers. For one company, an admin or owner on a Business, Enterprise or Edu plan adds your server as a custom MCP server, tests it and publishes it to that workspace only.¹⁸ Admins also decide which apps their workspace may use. In Business, many apps are on by default, and new Enterprise and Edu workspaces start with a selected set turned on.¹⁷

For everyone, you submit a plugin to ChatGPT's directory as a verified individual or organization, with a demo account for the reviewers. Plugins that need an extra sign-up step during review are rejected.¹⁹

Charging is the biggest difference. Inside ChatGPT, an app may sell only physical goods, with the checkout on your own website. It may not sell subscriptions, digital products, services or credits, show your plans or promote upgrades.¹⁹

An app may let a user sign in to an account they already pay for, and use what that subscription includes. If a feature needs a higher plan, the app may say so and link to a page that describes your plans, but not to a checkout page. It may not offer a weaker version than your own service, or add a fee that applies only in ChatGPT.¹⁹

So on OpenAI, customers subscribe on your website, outside ChatGPT, and the app only checks what they have paid for. This is the model on this page, with one difference: the app never sends anyone to a checkout for a subscription.

Design for both. When a signed-in user has not paid, return a short message and a link to your plans page, not to a checkout page. That one message works on both platforms.

In open source

MCP is an open standard, so open-source agents can connect to the same server. If you also run an open model yourself, you pay for the AI.

Part VI gives the full rules for all three, each with the date it was checked.