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An MCP service lets an agent use a remote MCP server, such as Linear’s or Notion’s, during a session. It’s one of the two types of service you can add to an access bundle. The other type, an HTTP service, covers a web API that the agent calls directly. You add the MCP server to your agent with its real URL and no credentials. When the agent connects to the server, the proxy attaches the service’s credential, so the agent can call the server’s tools without ever holding the credential.

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Prerequisites

  • The Admin role in Agent Vault
  • An access bundle to add the MCP server to
  • A running proxy that your agent can reach
  • An account with the MCP server’s provider, or a token the server accepts

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Add an MCP server

1
In Agent Vault, go to Access Bundles. Select your access bundle, then select Add Service.
2
On the Choose a template panel, pick a template under MCP Servers, or select Custom MCP Server to connect any other remote MCP server.
3
On the Details step, enter a Name, and check the Transport and Server URL. A template fills in the transport and server URL for you. Select Continue.
4
On the Credential step, pick a Credential Type and set up the credential. Select Continue.
5
On the Review step, select Add Service. The service appears in the bundle’s list with the type MCP Server.
Next, connect your agent to the MCP server.

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Server URL and transport

  • Server URL: The URL your agent connects to, such as https://mcp.linear.app/mcp (it must start with https://, and can’t include a username, password, query string, or fragment)
  • Transport: Streamable HTTP for most servers, or SSE if the server uses the older HTTP+SSE transport
The service covers every request to the server URL’s host, whatever the path. If the URL includes a port other than 443, the service covers only that port. Two services in the same access bundle can’t cover the same host, as described in host conflicts.

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Credential types

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OAuth

With OAuth, you sign in to the provider from Infisical, and Infisical stores the tokens the provider returns. If the provider also returns a refresh token, Infisical renews the access token before the token expires. If the provider doesn’t return one, reauthorize the service when the access token expires or the server rejects it. The proxy only receives the access token, and the agent never receives any token.
1
Under Credential Type, select OAuth, then select Authorize.
Some servers, such as GitHub’s, don’t let Infisical register itself as an OAuth client. For these servers, Infisical asks for an OAuth app of your own instead. Create an OAuth app with the provider, and set its redirect URI to the Redirect URI that Infisical shows. Then enter the app’s Client ID and Client Secret (leave Client Secret empty for a public client), and authorize again.
2
In the pop-up window, sign in to the provider and approve access.
3
When Infisical shows Authorized and the scopes the provider granted, select Continue. Continue stays disabled until the authorization succeeds.
Every session that uses the access bundle calls tools as the account you signed in with. Sign in with an account that has only the access your agents need.

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Bearer token

With a Bearer token, you paste a token the MCP server accepts into Token, such as a GitHub personal access token for GitHub MCP. The proxy sends the token as Authorization: Bearer <token>. To send the token in a different header or with a different prefix, expand Advanced Options and change Header Name or Prefix. To use a token that several services share, type {{ in Token and select a variable.

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Custom headers

If the MCP server needs another header besides the credential, such as an organization ID, add it as a custom header. The proxy adds custom headers to every request to the server, whichever auth method the service uses.
1
On the Credential step, expand Advanced Options and select Add Custom Header.
2
Enter the header’s Name, an optional Prefix, and the Value. To use a variable, type {{ in Value.
Infisical won’t save a custom header with the same name as the credential’s header, which is Authorization unless you changed a Bearer token’s Header Name. Infisical also won’t save a header that the proxy sets itself, such as Host or Content-Length.

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Connect your agent

1
Create a session for the access bundle, and copy the infisical agent-vault run command it gives you.
2
Add the MCP server to your agent by its server URL. Don’t add a token, and don’t sign in to the server from the agent.
If the service uses the SSE transport, use --transport sse instead.
3
Start the agent with the command from the session. For example, with Claude Code:
4
Ask the agent to use one of the server’s tools, such as listing your Linear issues. The call appears in the session’s logs with the tool name.

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Limitations

  • Remote servers only: An MCP service covers MCP servers that the agent reaches over HTTPS. A local MCP server that the agent starts as a process isn’t an MCP service, but you can add HTTP services for the APIs that the local server calls
  • No OAuth on private networks: Infisical connects to the MCP server and to the provider to set up OAuth and refresh the access token, so if either one is on a private network, use a Bearer token instead, or set ALLOW_INTERNAL_IP_CONNECTIONS to true if you self-host Infisical on that network
  • No tool filtering: The agent can call every tool the server offers to the credential, so limit what the agent can do through the credential’s own permissions
  • No connectors that run in a vendor’s cloud: Custom connectors in claude.ai or ChatGPT connect from the vendor’s servers, so their traffic never reaches your proxy
  • No WebSocket transports: The proxy doesn’t support WebSocket connections

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Troubleshooting

If the server rejects an OAuth service’s token, the proxy gets a fresh token from Infisical and sends the request again. If that doesn’t work, or if the server rejects a Bearer token, the proxy returns a 502 response to the agent. Its message says what to do:
  • The service needs to be reauthorized: The provider no longer accepts the service’s login, or the server asked for scopes the authorization lacks. The access bundle’s Services table shows Needs Reauthorization or Missing Scopes for the service. Open the service’s menu, select Edit, and continue to the Credential step. Select Reauthorize, sign in to the provider again, then continue and select Save.
  • Try again in a moment: The proxy couldn’t get a valid token from Infisical this time. Try the tool call again.
  • The service’s credential was rejected: The server rejected the service’s Bearer token. Edit the service and paste a new token.
The redirect URI that Infisical gives the provider is your instance’s SITE_URL followed by /agent-vault/oauth/callback. Check that:
  • SITE_URL is set to the URL you use to open Infisical
  • SITE_URL uses https:// (providers such as Linear refuse a redirect URI on plain http:// unless the host is localhost)
The request reached the server without a credential. Check that:
  • The agent runs through infisical agent-vault run with a session for the access bundle
  • The server URL in the agent has the same host as the service’s Server URL