# LangChain TypeScript

## Install

```bash
npm install @langchain/mcp-adapters
```

---

## Connect

```typescript
import { MultiServerMCPClient } from "@langchain/mcp-adapters";

const MEWCP_API_KEY = "API_KEY";

async function main() {
  const client = new MultiServerMCPClient({
    mcpServers: {
      mewcp: {
        url: "https://gateway.mewcp.com/personal/mcp",
        headers: {
          Authorization: `Bearer ${MEWCP_API_KEY}`,
        },
      },
    },
  });

  const tools = await client.getTools();
  console.log(
    "Available tools:",
    tools.map((t) => t.name),
  );
  // -> ["search", "get_schema", "list_accounts", "call_tool"]

  await client.close();
}

main();
```

You get four tools rather than the tools of each app. Your agent uses them to reach every app you have connected. See [How MewCP works](/mewcp/getting-started#how-mewcp-works).

---

## Call a tool directly

```typescript
const callTool = tools.find((t) => t.name === "call_tool")!;

const result = await callTool.invoke({
  server_maskedId: "google-calendar",
  tool_name: "list_events",
  args: {
    calendar_id: "primary",
    time_min: "2026-01-15T00:00:00Z",
    time_max: "2026-01-16T00:00:00Z",
  },
});
console.log(result);
```

If you have connected more than one account for the same app, add `alias: "work"` to select one.

---

## Use with a LangChain agent

Hand all four tools to the agent and let it work out the rest:

```typescript
import { MultiServerMCPClient } from "@langchain/mcp-adapters";
import { ChatOpenAI } from "@langchain/openai";
import { createReactAgent } from "@langchain/langgraph/prebuilt";
import { HumanMessage } from "@langchain/core/messages";

async function main() {
  const client = new MultiServerMCPClient({
    mcpServers: {
      mewcp: {
        url: "https://gateway.mewcp.com/personal/mcp",
        headers: { Authorization: `Bearer ${MEWCP_API_KEY}` },
      },
    },
  });

  const tools = await client.getTools();
  const model = new ChatOpenAI({ model: "gpt-4o" });
  const agent = createReactAgent({ llm: model, tools });

  const result = await agent.invoke({
    messages: [new HumanMessage("What is on my calendar tomorrow?")],
  });
  console.log(result.messages.at(-1)?.content);

  await client.close();
}

main();
```

The agent will call `search` to find the calendar tool, `get_schema` for its parameters, then `call_tool` to run it.

---

## Where to find your values

| Value          | Where to get it       |
| -------------- | --------------------- |
| `API_KEY`      | Dashboard -> API Keys |
| Connected apps | Dashboard -> Servers  |