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58 lines
2.0 KiB
Markdown
58 lines
2.0 KiB
Markdown
# MCP
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[Model Context Protocol (MCP)](https://modelcontextprotocol.io/introduction) is an open protocol that standardizes how applications provide tools and context to language models. LangGraph agents can use tools defined on MCP servers through the `langchain-mcp-adapters` library.
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Install the `langchain-mcp-adapters` library to use MCP tools in LangGraph:
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```bash
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pip install langchain-mcp-adapters
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```
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## Authenticate to an MCP server
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You can set up [custom authentication middleware](../how-tos/auth/custom_auth.md) to authenticate a user with an MCP server to get access to user-scoped tools within your LangGraph Platform deployment.
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!!! note
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Custom authentication is a LangGraph Platform feature.
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An example architecture for this flow:
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```mermaid
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sequenceDiagram
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%% Actors
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participant ClientApp as Client
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participant AuthProv as Auth Provider
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participant LangGraph as LangGraph Backend
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participant SecretStore as Secret Store
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participant MCPServer as MCP Server
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%% Platform login / AuthN
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ClientApp ->> AuthProv: 1. Login (username / password)
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AuthProv -->> ClientApp: 2. Return token
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ClientApp ->> LangGraph: 3. Request with token
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Note over LangGraph: 4. Validate token (@auth.authenticate)
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LangGraph -->> AuthProv: 5. Fetch user info
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AuthProv -->> LangGraph: 6. Confirm validity
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%% Fetch user tokens from secret store
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LangGraph ->> SecretStore: 6a. Fetch user tokens
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SecretStore -->> LangGraph: 6b. Return tokens
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Note over LangGraph: 7. Apply access control (@auth.on.*)
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%% MCP round-trip
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Note over LangGraph: 8. Build MCP client with user token
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LangGraph ->> MCPServer: 9. Call MCP tool (with header)
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Note over MCPServer: 10. MCP validates header and runs tool
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MCPServer -->> LangGraph: 11. Tool response
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%% Return to caller
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LangGraph -->> ClientApp: 12. Return resources / tool output
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```
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For more information, see [MCP endpoint in LangGraph Server](../concepts/server-mcp.md#use-user-scoped-mcp-tools-in-your-deployment).
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