Tools and connections

Tools are what an agent can act on. Your own functions, the tools of an MCP server, or another service the user has signed in to.

Why they need more than the AI SDK's tool()

A tool in a product acts for one customer, often with that customer's credentials. Three things have to be right: the tool reaches only that customer's data, the credential never reaches the model, and a user who hasn't signed in to a service is asked to, instead of the agent failing.

Your own tools

Plain AI SDK tools. They receive the context, so they act for the right customer:

const refund = tool({
  description: "Refund an order",
  inputSchema: z.object({ orderId: z.string() }),
  execute: async ({ orderId }, { context }) =>
    (context as ToolContext<Principal, Ctx>).orders.refund(orderId),
});

Connections: tools from other services

Name a service on the agent, and its tools appear for each person who has access:

import { createMcpConnections, oauth } from "@intentface/latch-mcp";

createRuntime({
  …,
  connections: createMcpConnections({
    vault,
    allowedHosts: ["mcp.linear.app"],
    callbackBaseUrl: "https://app.example.com/api/latch/connections",
    connections: { linear: { url: "https://mcp.linear.app/mcp", auth: oauth() } },
  }),
});

defineAgent({ …, connections: ["linear"] });

A user who hasn't connected Linear yet sees the agent ask them to, and the conversation continues after they sign in. Their tokens are stored encrypted in the vault and used on their behalf; the model never sees them. Tools the server marks as destructive need approval by default; servers don't always mark them, so you can ask for approval on every tool instead.

Secrets for your own tools

The same vault holds API keys your tools need, per customer. A tool reads one when it runs and returns only the result:

const key = await vault.get({ orgId: principal.orgId }, "crm_api_key");

Setup, team and personal keys, and what protects them: Secrets (the vault).

Go deeper

• What signing in involves: Connecting accounts
• OpenAPI specs as tools: @intentface/latch-openapi