> For the complete documentation index, see [llms.txt](https://docs.stackai.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.stackai.com/guides-and-quickstarts/using-tools-and-actions/mcp-tools-in-an-agent.md). # MCP tools in an agent Model Context Protocol (MCP) servers make external tools available to an agent. An agent can use those tools to retrieve information or perform actions while answering a request. {% embed url="" %} ## Before you start Open an editable agent. For a catalog server, have an account with the required provider access. For a custom server, obtain its endpoint, authentication requirements, and required headers from its owner before setup. Review [Give an agent tools](/guides-and-quickstarts/agent-builder-and-skills/give-an-agent-tools.md) for the agent-side tool configuration. ## Describe how the agent should use tools Give the agent a clear instruction for when to use the external tools. ![Agent tool use instructions](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/ikZ0Z92EIgIPsj8zaXGg/assets/g051-g051-01-prompt.png) State whether it should only retrieve information or may also change records. ## Connect a catalog MCP server In MCP Servers, add the required catalog integration. ![Catalog MCP server connection](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/cUyVy4YMGliaCa0wXt4j/assets/g051-g051-02-catalog.png) A catalog entry identifies the service but does not by itself authorize an account. Complete the provider authorization with the intended account. ![Catalog MCP server connection](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/63yEXgPve5gBwAaaQWX6/assets/g051-g051-03-consent.png) Review the requested access before making the server available to the agent. Inspect the server's available tools and connection mode. ![Catalog MCP server connection](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/UlMzdNHWXGwIOEqDPHnO/assets/g051-g051-04-tools.png) Confirm that the agent has the tools needed for its task and understand which account they use. ## Review a tool call Run a request that requires a tool and expand the tool trace. ![Agent tool call trace](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/E0sWnrjERxJzfk101ev1/assets/g051-g051-05-trace.png) Check the tool name, arguments, and returned data against the final answer. ## Connect a custom MCP server Choose Add custom MCP configuration for your own server. ![Custom MCP server configuration](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/Du818qn1UEEUkrNPIv9u/assets/g051-g051-06-custom.png) Enter its authorized endpoint, a stable label, and a description of when the agent should use it. Use the supported secret reference for authentication. ![Custom MCP server configuration](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/wX2ipXuPONZMoZnOhhXq/assets/g051-g051-07-secret.png) Keep the credential in the designated secret store rather than in instructions or shared text. Add the headers required by the server and save the configuration. ![Custom MCP server configuration](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/sbQRdTIf2aodadeTZEAS/assets/g051-g051-08-headers.png) Check header names and values against that server's connection requirements. ## Check and review the custom connection Run a request through the custom server and inspect the tool response. ![Custom MCP connection verification](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/xfrBo4Lrjvp3Dw4woyAI/assets/g051-g051-09-custom-trace.png) Verify both endpoint access and the data used by the agent's answer. Reopen the saved configuration to review the endpoint, label, authentication reference, and headers. ![Custom MCP connection verification](https://content.gitbook.com/content/SQ1Sgy933krTyK0S4JpP/blobs/1ub31NLf9bpKAiikwkp8/assets/g051-g051-10-review.png) Confirm the saved values before using the server in a broader workflow. ## Important behavior MCP lets an agent discover and call tools exposed by another service. The server and connected account determine which operations and data are available. Store authentication credentials in the supported secret store. Reference those secrets in the server configuration. ## Continue * [End user connections](/guides-and-quickstarts/using-tools-and-actions/end-user-connections.md) * [Give an agent tools](/guides-and-quickstarts/agent-builder-and-skills/give-an-agent-tools.md) --- # Agent Instructions This documentation is published with GitBook. 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