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You can connect Agent Builder to third-party MCP servers to extend your agents with additional tools and integrations. This page covers how to add custom MCP servers and provides configuration details for popular third-party servers.

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Add a third-party MCP server

To connect a third-party MCP server to Agent Builder:
1

Navigate to MCP server settings

In the LangSmith UI, select Settings in the lower left sidebar, then choose the MCP Servers tab.
2

Add the server

Click Add server and enter:
  • Name: A descriptive name for the server
  • URL: The MCP server endpoint URL
3

Configure authentication

Select an authentication type based on the server’s requirements:
  • Headers: Add key-value pairs sent with every request. Use {{SECRET_NAME}} placeholders to reference workspace secrets.
  • OAuth 2.1 (Auto): Select this for servers that support OAuth. You’ll be prompted to log in with your account for that service.
For specific authentication details, see the configuration details for each supported server.
4

Add headers (optional)

If your MCP server requires additional headers, click Add headers and enter the key and value.
5

Save and verify

Click Save server. Agent Builder will discover available tools from the server.

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Supported servers

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Arcade

Arcade provides a gateway for connecting to various tools and services. Configuration details Option 1: Headers authentication Add the following headers: Store your Arcade API key as a workspace secret named ARCADE_API_KEY. Option 2: OAuth authentication
  1. Select OAuth 2.1 (Auto) as the auth type when adding the server.
  2. Log in with your Arcade account when prompted.
To learn more about Arcade MCP integration, see the Arcade documentation.

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Parallel

Parallel provides search and task automation tools. Configuration details Add the following header: Store your Parallel API key as a workspace secret named PARALLEL_API_KEY. For more information, see the Parallel documentation for search MCP and task MCP.

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Notion

Notion provides tools for interacting with your Notion workspace. Configuration details
  1. Select OAuth 2.1 (Auto) as the auth type when adding the server.
  2. Log in with your Notion account when prompted.
For more information, see the Notion MCP documentation.
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