docs: add LangChain integration page to MCP Toolkit section

SUMMARY.md

@@ -22,6 +22,7 @@
   * [Get Started](ai/mcp-toolkit/get-started.md)
   * [Configuration](ai/mcp-toolkit/configuration.md)
   * [API Reference](ai/mcp-toolkit/api-reference.md)
+  * [LangChain Integration](ai/mcp-toolkit/langchain.md)
 * [Agent Skills](ai/agent-skills.md)
 * [OpenClaw](ai/openclaw.md)
 * [x402](ai/x402.md)

ai/mcp-toolkit/README.md

@@ -107,6 +107,18 @@ You can register **any** blockchain name - the `CHAINS` constants are for conven
 				<a href="./api-reference.md">api-reference.md</a>
 			</td>
 		</tr>
+		<tr>
+			<td>
+				<i class="fa-link">:link:</i>
+			</td>
+			<td>
+				<strong>LangChain Integration</strong>
+			</td>
+			<td>Use WDK tools in LangChain agents via the serve CLI</td>
+			<td>
+				<a href="./langchain.md">langchain.md</a>
+			</td>
+		</tr>
 	</tbody>
 </table>
 

ai/mcp-toolkit/get-started.md

@@ -20,6 +20,10 @@ layout:
 
 # Get Started
 
+{% hint style="info" %}
+**Building a LangChain agent?** The `serve` command provides zero-config MCP server startup -- no server script needed. See [LangChain Integration](langchain.md).
+{% endhint %}
+
 ## Setup Wizard
 
 The fastest way to get running. Clone the repository and let the wizard configure everything:

ai/mcp-toolkit/langchain.md

@@ -0,0 +1,290 @@
+---
+title: LangChain Integration
+description: Use WDK MCP tools in LangChain agents with zero-config server startup
+icon: link
+layout:
+  width: default
+  title:
+    visible: true
+  description:
+    visible: true
+  tableOfContents:
+    visible: true
+  outline:
+    visible: true
+  pagination:
+    visible: true
+  metadata:
+    visible: false
+---
+
+# LangChain Integration
+
+You can use the WDK MCP Toolkit as a tool provider for [LangChain](https://www.langchain.com/) agents in both Python and TypeScript. LangChain's `MultiServerMCPClient` spawns the MCP server as a subprocess and converts WDK tools into LangChain-compatible tools, giving your agent access to wallet operations, pricing, swaps, bridges, lending, and more.
+
+This integration uses the `serve` CLI command, which starts a fully configured MCP server on stdio with no server script required.
+
+{% hint style="info" %}
+This approach uses LangChain's MCP adapters to connect to the WDK MCP server. WDK does not ship a native LangChain integration, it leverages the standard MCP protocol that LangChain already supports.
+{% endhint %}
+
+{% hint style="info" %}
+**Want more control?** The `serve` command is the fastest way to get running, but you can also [write your own MCP server](get-started.md#manual-setup) with the programmatic API for full control over wallets, tools, and protocols. Then point LangChain's `MultiServerMCPClient` at it using `node your-server.js` instead of the `serve` command.
+{% endhint %}
+
+***
+
+## The `serve` Command
+
+The `serve` command provides zero-config MCP server startup so you don't need to write a server script:
+
+{% code title="Terminal" %}
+```bash
+npx @tetherto/wdk-mcp-toolkit serve
+```
+{% endcode %}
+
+Pass `WDK_SEED` to enable wallet operations, or omit it to run with pricing tools only:
+
+{% code title="Terminal" %}
+```bash
+# With wallet operations
+WDK_SEED="your twelve word seed phrase here" npx @tetherto/wdk-mcp-toolkit serve
+
+# Pricing-only mode (no seed required)
+npx @tetherto/wdk-mcp-toolkit serve
+```
+{% endcode %}
+
+### Default Chains
+
+By default, `serve` enables **three chains**: Ethereum, Arbitrum, and Bitcoin. For each enabled chain it dynamically imports the required wallet package and skips any that aren't installed. You can change the enabled set with the `WDK_CHAINS` environment variable.
+
+### Built-in Registry
+
+The command has built-in definitions for 13 chains and 4 protocol modules. When a chain is enabled and its package is installed, the wallet is registered automatically. Protocol modules are also auto-registered when their packages are installed and at least one of their target chains is enabled.
+
+| Module | Registers | Default |
+| --- | --- | --- |
+| [`@tetherto/wdk-wallet-evm`](https://docs.wdk.tether.io/sdk/wallet-modules/wallet-evm) | Ethereum, Arbitrum, Polygon, Optimism, Base, Avalanche, BNB, Plasma, Spark | Ethereum + Arbitrum enabled |
+| [`@tetherto/wdk-wallet-btc`](https://docs.wdk.tether.io/sdk/wallet-modules/wallet-btc) | Bitcoin | Enabled |
+| [`@tetherto/wdk-wallet-solana`](https://docs.wdk.tether.io/sdk/wallet-modules/wallet-solana) | Solana | Not enabled by default |
+| [`@tetherto/wdk-wallet-ton`](https://docs.wdk.tether.io/sdk/wallet-modules/wallet-ton) | TON | Not enabled by default |
+| [`@tetherto/wdk-wallet-tron`](https://docs.wdk.tether.io/sdk/wallet-modules/wallet-tron) | Tron | Not enabled by default |
+| [`@tetherto/wdk-protocol-swap-velora-evm`](https://docs.wdk.tether.io/sdk/swap-modules/swap-velora-evm) | Swap tools (Ethereum, Arbitrum) | -- |
+| [`@tetherto/wdk-protocol-bridge-usdt0-evm`](https://docs.wdk.tether.io/sdk/bridge-modules/bridge-usdt0-evm) | Bridge tools (Ethereum, Arbitrum) | -- |
+| [`@tetherto/wdk-protocol-lending-aave-evm`](https://docs.wdk.tether.io/sdk/lending-modules/lending-aave-evm) | Lending tools (Ethereum) | -- |
+| [`@tetherto/wdk-protocol-fiat-moonpay`](https://docs.wdk.tether.io/sdk/fiat-modules/fiat-moonpay) | Fiat tools (Ethereum) | Requires `MOONPAY_*` env vars |
+
+{% hint style="info" %}
+Missing packages are silently skipped. Install only the modules you need and `serve` will pick them up. For chains or protocols **not** in the built-in registry, use a [custom config file](#custom-config-file).
+{% endhint %}
+
+***
+
+## Quick Start
+
+{% tabs %}
+{% tab title="Python" %}
+
+#### Install dependencies
+
+{% code title="Terminal" %}
+```bash
+pip install langchain-mcp-adapters langgraph langchain-openai
+```
+{% endcode %}
+
+#### Create your agent
+
+{% code title="agent.py" lineNumbers="true" %}
+```python
+import asyncio
+from langchain_mcp_adapters.client import MultiServerMCPClient
+from langgraph.prebuilt import create_react_agent
+from langchain_openai import ChatOpenAI
+
+async def main():
+    client = MultiServerMCPClient({
+        "wdk": {
+            "transport": "stdio",
+            "command": "npx",
+            "args": ["-y", "@tetherto/wdk-mcp-toolkit", "serve"],
+            "env": {
+                "WDK_SEED": "your twelve word seed phrase here",
+                "WDK_MCP_ELICITATION": "false",
+            },
+        }
+    })
+
+    tools = await client.get_tools()
+    agent = create_react_agent(ChatOpenAI(model="gpt-4o"), tools)
+
+    result = await agent.ainvoke({
+        "messages": [{"role": "user", "content": "What is my Ethereum address?"}]
+    })
+    print(result["messages"][-1].content)
+
+    await client.close()
+
+asyncio.run(main())
+```
+{% endcode %}
+
+#### Run it
+
+{% code title="Terminal" %}
+```bash
+export OPENAI_API_KEY="sk-..."
+python agent.py
+```
+{% endcode %}
+
+{% endtab %}
+{% tab title="TypeScript" %}
+
+#### Install dependencies
+
+{% code title="Terminal" %}
+```bash
+npm install @langchain/mcp-adapters @langchain/langgraph @langchain/core @langchain/openai
+```
+{% endcode %}
+
+#### Create your agent
+
+{% code title="agent.ts" lineNumbers="true" %}
+```typescript
+import { MultiServerMCPClient } from "@langchain/mcp-adapters";
+import { createReactAgent } from "@langchain/langgraph/prebuilt";
+import { ChatOpenAI } from "@langchain/openai";
+
+const client = new MultiServerMCPClient({
+  wdk: {
+    transport: "stdio",
+    command: "npx",
+    args: ["-y", "@tetherto/wdk-mcp-toolkit", "serve"],
+    env: {
+      WDK_SEED: "your twelve word seed phrase here",
+      WDK_MCP_ELICITATION: "false",
+    },
+  },
+});
+
+const tools = await client.getTools();
+const agent = createReactAgent({
+  llm: new ChatOpenAI({ model: "gpt-4o" }),
+  tools,
+});
+
+const result = await agent.invoke({
+  messages: [
+    { role: "user", content: "What is the current price of Bitcoin?" },
+  ],
+});
+
+console.log(result.messages[result.messages.length - 1].content);
+await client.close();
+```
+{% endcode %}
+
+#### Run it
+
+{% code title="Terminal" %}
+```bash
+export OPENAI_API_KEY="sk-..."
+npx tsx agent.ts
+```
+{% endcode %}
+
+{% endtab %}
+{% endtabs %}
+
+{% hint style="warning" %}
+**Security** -- Always use a dedicated development wallet with limited funds. Set `WDK_MCP_ELICITATION` to `"false"` for programmatic agents since elicitation dialogs require a human in the loop.
+{% endhint %}
+
+***
+
+## Configuration
+
+### Environment Variables
+
+Control `serve` behavior through environment variables:
+
+| Variable | Required | Default | Description |
+| --- | --- | --- | --- |
+| `WDK_SEED` | No | -- | BIP-39 seed phrase. If omitted, only pricing tools are available |
+| `WDK_CHAINS` | No | `ethereum,arbitrum,bitcoin` | Comma-separated list of chains to enable |
+| `WDK_MCP_ELICITATION` | No | `true` | Set to `"false"` for programmatic agents that cannot handle confirmation dialogs |
+| `WDK_RPC_<CHAIN>` | No | Built-in defaults | Override the RPC endpoint for a chain (e.g. `WDK_RPC_ETHEREUM=https://my-rpc.com`) |
+| `WDK_CONFIG` | No | -- | Path to a `wdk.config.json` file for custom chains and protocols |
+| `WDK_INDEXER_API_KEY` | No | -- | Enables indexer tools for balance and transfer history queries |
+| `MOONPAY_API_KEY` | No | -- | Enables fiat on/off-ramp tools |
+| `MOONPAY_SECRET_KEY` | No | -- | Required with `MOONPAY_API_KEY` |
+
+### Custom Config File
+
+For chains or protocols not in the built-in defaults, create a `wdk.config.json` and pass its path via `WDK_CONFIG`:
+
+{% code title="Terminal" %}
+```bash
+WDK_CONFIG=./wdk.config.json WDK_SEED="..." npx @tetherto/wdk-mcp-toolkit serve
+```
+{% endcode %}
+
+{% code title="wdk.config.json" %}
+```json
+{
+  "chains": {
+    "zksync": {
+      "module": "@myorg/wdk-wallet-zksync",
+      "config": { "provider": "https://mainnet.era.zksync.io" }
+    },
+    "ethereum": {
+      "config": { "provider": "https://my-private-rpc.com" }
+    }
+  },
+  "protocols": [
+    {
+      "module": "@myorg/wdk-protocol-swap-custom",
+      "label": "custom-swap",
+      "type": "swap",
+      "chains": ["zksync"]
+    }
+  ],
+  "enabledChains": ["ethereum", "zksync", "bitcoin"]
+}
+```
+{% endcode %}
+
+| Field | Description |
+| --- | --- |
+| `chains` | Add new chains or override config for built-in ones. New chains require a `module` field; overrides for existing chains can omit it |
+| `protocols` | Add custom protocols. Each entry requires `module`, `label`, and `chains`. The `type` field (`swap`, `bridge`, `lending`, `fiat`) maps to the corresponding built-in tool set |
+| `enabledChains` | Overrides `WDK_CHAINS` env var. If omitted, `WDK_CHAINS` is used |
+
+***
+
+## LLM Provider Support
+
+Both the Python and TypeScript examples support OpenAI and Anthropic. Set the corresponding environment variable and install the matching package:
+
+| Provider | Environment Variable | Python Package | TypeScript Package |
+| --- | --- | --- | --- |
+| OpenAI | `OPENAI_API_KEY` | `langchain-openai` | `@langchain/openai` |
+| Anthropic | `ANTHROPIC_API_KEY` | `langchain-anthropic` | `@langchain/anthropic` |
+
+{% hint style="info" %}
+The examples auto-detect which provider to use based on which API key is set. If both are set, OpenAI takes priority.
+{% endhint %}
+
+{% hint style="success" %}
+**Full examples** -- See the complete interactive agent examples with conversation loops on GitHub: [`examples/langchain/python/`](https://github.com/tetherto/wdk-mcp-toolkit/tree/main/examples/langchain/python) and [`examples/langchain/typescript/`](https://github.com/tetherto/wdk-mcp-toolkit/tree/main/examples/langchain/typescript).
+{% endhint %}
+
+***
+
+## Need Help?
+
+{% include "../../.gitbook/includes/support-cards.md" %}