# How to Connect the Vercel AI SDK to MewCP

The AI SDK's MCP client turns MewCP's tools into AI SDK tools you pass to `generateText` or `streamText`. Your agent then reaches every app connected to its toolset through one HTTP connection.

---

## Before you start

- **Node.js 18 or newer** and a TypeScript project
- **A toolset and its key.** See [Choose a toolset](/mewcp/frameworks#choose-a-toolset)
- **Your environment** set as in [Set your environment](/mewcp/frameworks#set-your-environment):

  ```bash
  MEWCP_MCP_URL=https://gateway.mewcp.com/personal/mcp
  MEWCP_API_KEY=API_KEY
  ```

---

## Install

```bash
npm install ai @ai-sdk/mcp
```

The examples use an [AI Gateway](https://ai-sdk.dev/providers/ai-sdk-providers/ai-gateway) model string. Any model provider the AI SDK supports works the same way.

---

## Connect

```ts
import { createMCPClient } from "@ai-sdk/mcp";
import { generateText, isStepCount } from "ai";

const mcp = await createMCPClient({
  transport: {
    type: "http",
    url: process.env.MEWCP_MCP_URL!,
    headers: { Authorization: `Bearer ${process.env.MEWCP_API_KEY}` },
  },
});

try {
  const tools = await mcp.tools();

  const { text } = await generateText({
    model: "anthropic/claude-sonnet-5.5",
    tools,
    // MewCP takes several tool calls per answer: search, get_schema, call_tool.
    stopWhen: isStepCount(10),
    prompt: "What is on my calendar tomorrow?",
  });

  console.log(text);
} finally {
  await mcp.close();
}
```

Keep `stopWhen`. Without it, `generateText` and `streamText` stop after one step, so the agent finds a tool with `search` and never runs it.

---

## Serve your users

With a project toolset, add `x-mewcp-enduser-id` to the transport headers, set to the user the agent is acting for. Create the client per request, so each user's calls carry their own ID:

```ts
import { createMCPClient } from "@ai-sdk/mcp";
import { generateText, isStepCount } from "ai";

export async function answerFor(userId: string, prompt: string) {
  const mcp = await createMCPClient({
    transport: {
      type: "http",
      url: process.env.MEWCP_MCP_URL!,
      headers: {
        Authorization: `Bearer ${process.env.MEWCP_API_KEY}`,
        "x-mewcp-enduser-id": userId,
      },
    },
  });

  try {
    const { text } = await generateText({
      model: "anthropic/claude-sonnet-5.5",
      tools: await mcp.tools(),
      stopWhen: isStepCount(10),
      prompt,
    });
    return text;
  } finally {
    await mcp.close();
  }
}
```

Use the same ID you pass as `externalUserId` when the user connects their accounts through the [MewCP Auth API](/mewcp-auth). If they have not connected the app a tool needs, the tool result carries a link for them to connect it, and the model can pass it on.

Run this on your server, for example in a route handler. The key must never reach the browser.

---

## Check it works

List the tools before handing them to the model:

```ts
const tools = await mcp.tools();
console.log(Object.keys(tools));
// [ 'search', 'get_schema', 'list_accounts', 'call_tool' ]
```

Four tools, not the tools of every app, is expected. See [What your agent sees](/mewcp/frameworks#what-your-agent-sees).

---

## In production

- **Close the client.** Close it when the response is done: in `finally` for `generateText`, or in the `onEnd` callback for `streamText`.
- **Leave `maxRetries` off.** The client can retry failed tool calls, but `call_tool` runs actions such as sending an email, and a retry can repeat them.
- **Approve risky calls.** Pass a [`toolApproval`](https://ai-sdk.dev/docs/agents/tool-approvals) policy to `generateText` or `streamText` if a person should confirm before the agent acts.

---

## Troubleshooting

### The agent searches for a tool and then stops

`stopWhen` is missing or too low. Set `stopWhen: isStepCount(10)` so the model can run `search`, `get_schema` and `call_tool` in one answer.

### `createMCPClient` throws an `MCPClientError` with status `401` or `403`

MewCP rejected the key.

- Check `MEWCP_API_KEY` is set where the code runs, and the header reads `Bearer ` followed by the whole key.
- Check the key matches the toolset in `MEWCP_MCP_URL`: your API Key for the personal toolset, the project's key for a project toolset.
- A `403` that says the billing period is not active means your MewCP plan needs renewing in the dashboard.

### Calls run against the wrong user's accounts

Each client sends the `x-mewcp-enduser-id` it was created with. Do not share one client across users: create it inside the request, as in [Serve your users](#serve-your-users).

---

_Last checked against the AI SDK's documentation on 13 October 2026._