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Connect another MCP server

You can point MCP Studio at another MCP server and have its content answer questions alongside your own documentation. If that server needs an API key, you can paste one and MCP Studio will authenticate for you.

AudienceAnyone combining a hosted MCP server with their own sources
PrerequisitesThe server's endpoint URL, and its API key if it needs one

Why connect another MCP server​

If a tool you use already publishes an MCP server, that server is usually the best available source of truth for its own content. Connecting it through MCP Studio lets you build on that foundation in four useful ways.

One endpoint for several useful sources. Every MCP server you connect to an AI client is another entry in that client's config. Combining sources into a single MCP Studio server gives you one URL to share with your team and one place to update it later.

Answers that span sources. Your documentation explains the product, while your repositories can add practical examples from the same product. When both are sources on one server, a single question can draw from your published guidance and your code.

Current content from the source. A federated MCP source is queried at the moment the question is asked. This complements indexed sources particularly well for changelogs, status pages, and documentation that changes often.

Usage you can learn from. Every question that reaches your MCP server is recorded, including the ones answered by a federated source. Connecting a vendor's MCP server through MCP Studio gives you an additional view into what your team asks and which sources help. See Monitor quality and impact.

There are two practical details to keep in mind. A federated source adds a network round trip to the request, and only retrieval is forwarded. See What federation can and cannot do.

How this differs from other sources​

Every other source is crawled: MCP Studio fetches the pages once, indexes them, and answers from that index. An MCP server source is not crawled. Each question is forwarded to that server live, and its answer is combined with your indexed content.

That has two consequences worth knowing up front:

  • The content is always current, because nothing is cached.
  • If that server is down or slow, it simply contributes nothing to that answer. Your MCP server still responds using its other sources.

Add a public MCP server​

Many hosted MCP servers need no credentials. Most documentation servers are one example.

  1. In the Sources step, paste the endpoint URL. Most look like https://mcp.example.com/mcp.
  2. MCP Studio recognises it as an MCP endpoint and asks whether it requires authentication. Choose No, it's public.
  3. MCP Studio connects and shows you the tools that server offers.
  4. Click Add this source.

If the endpoint does not answer as an MCP server, you are told so and offered Add as a website instead. This is useful when the URL turned out to be a documentation page about MCP rather than an endpoint.

Example: a GitBook documentation site​

Every published GitBook site has a public MCP server. Take the published site URL and add /~gitbook/mcp:

https://gitbook.com/docs  →  https://gitbook.com/docs/~gitbook/mcp

No key is needed. MCP Studio will show tools such as searchDocumentation and askQuestion, and questions your agent asks are answered from that site's current published content.

Two things to check if it does not connect:

  • The site must be published. The MCP server only exposes published content.
  • Page actions must be enabled in GitBook under Site customization. With them off, GitBook disables the endpoint and it returns a 404.

If the GitBook site itself requires a login, use /~gitbook/mcp/auth instead. That endpoint expects an OAuth sign-in rather than an API key, which MCP Studio does not support yet. See the limits below.

When a server needs additional context​

Some MCP servers require an identifier on every tool that a search question does not carry. DeepWiki, for instance, needs a repository name; Context7 needs you to resolve a library id first. MCP Studio connects to these successfully and lists their tools, but a plain question does not include the additional value those tools need.

When that happens the wizard tells you before you add the source: these tools all need extra details we can't infer from a search. You can still add it. Nothing breaks, but that server may be more useful when connected directly to an AI client that can collect those details from you.

This is why the connection screen shows the tool list. If the tools look like they need parameters you would normally type by hand, you can choose the connection that best fits your workflow.

Add an authenticated MCP server​

  1. Paste the endpoint URL and choose Yes, it needs a key.
  2. Pick the header the server expects. Most use Authorization: Bearer; some use X-API-Key.
  3. Paste your API key. Paste just the key. MCP Studio adds the Bearer prefix for you.
  4. Click Test connection. If the server rejects the key, you can try another one without leaving the step.
  5. Click Add this source.
Authenticated sources make your server private

Because MCP Studio reaches this source using your key, it can return content that someone without that key could not fetch. Your MCP server is therefore created as private: its endpoint refuses any request that does not carry an access token, which MCP Studio generates for you when you deploy. See Private MCP servers.

This cannot be switched back to public while the authenticated source is attached. Removing the key does not switch it back either, because content that key could reach has already been indexed.

How your key is stored​

  • It is encrypted at rest with AES-256-GCM. The encryption key is held in MCP Studio's environment, never in the database, so a database copy on its own is not enough to use your key.
  • It is sent only to the endpoint you added it for. If that endpoint redirects to a different domain, the key is deliberately not forwarded.
  • It is never shown again after you save it, and it is never included in any API response or dashboard page.
  • It is not saved in your browser. If you reload the page part-way through creating a server, you will be asked for the key again.

Change or remove a key​

Open your server on the dashboard, find the source, and click Key.

  • Paste a new key and choose Save and verify to replace the stored one.
  • Choose Remove key to delete it. The source stays, but stops authenticating.

Changing a key does not use one of your paid source slots.

What "verified" means

MCP Studio checks that the server does not reject your key when listing its tools. Some servers accept any value at that stage and only check the key when a tool actually runs, so a successful test means your key was not refused rather than proof it is valid. MCP Studio will not run one of that server's tools to check, because doing so could have real effects, such as sending an email.

What federation can and cannot do​

MCP Studio uses the remote server's tools for retrieval: finding and reading content to answer a question.

It does not expose that server's action tools to your AI client. If the server you connect can send an email or open a pull request, your agent cannot ask it to do those things through MCP Studio. Only searching and reading are forwarded.

This is a deliberate limit. An MCP server that both reads untrusted content and holds credentials to take actions can be manipulated by that content, so MCP Studio does not combine the two.

Two more practical limits:

  • A remote answer is shortened. MCP Studio keeps up to about 6,000 characters from each MCP source per question, so that a long reply cannot crowd out your indexed content. Ask a narrower question if you need more detail.
  • Each source has a response window. Each MCP source gets about 12 seconds. Servers that answer with a model can take longer than that, in which case MCP Studio uses that server's faster search tool.

Servers that require parameters on every tool are covered in When a server needs additional context.

When a source shows an error​

MessageWhat to do
Needs credentials, or the key was rejectedClick Update key on the source and paste a current key
Did not respondCheck the endpoint URL, then Refresh the source
Answered, but not as an MCP serverThe URL is probably not an endpoint. Remove it and add it as a website

For a GitBook site returning "did not respond", confirm the site is published and that Page actions are enabled. GitBook returns a 404 for the endpoint when they are off.