Connect Sanity Context with LangChain

npm install langchain@^1 @langchain/mcp-adapters@^2 @langchain/anthropic@^1 @langchain/core@^1

pnpm add langchain@^1 @langchain/mcp-adapters@^2 @langchain/anthropic@^1 @langchain/core@^1

yarn add langchain@^1 @langchain/mcp-adapters@^2 @langchain/anthropic@^1 @langchain/core@^1

bun add langchain@^1 @langchain/mcp-adapters@^2 @langchain/anthropic@^1 @langchain/core@^1

The example uses version 2 of @langchain/mcp-adapters, which includes its own MCP client, so you don't install the MCP SDK separately. Set the module type in package.json so Node.js loads agent.ts as an ES module:

npm pkg set type=module

If you type-check with tsc, set "skipLibCheck": true in tsconfig.json. Recent @langchain/anthropic releases fail library checks against newer @anthropic-ai/sdk types.

import {createAgent} from 'langchain'
import {ChatAnthropic} from '@langchain/anthropic'
import {MCPAdapter} from '@langchain/mcp-adapters'

const MCP_URL = process.env.SANITY_CONTEXT_MCP_URL
const API_TOKEN = process.env.SANITY_ORGANIZATION_TOKEN
if (!MCP_URL || !API_TOKEN) {
  throw new Error('Set SANITY_CONTEXT_MCP_URL and SANITY_ORGANIZATION_TOKEN')
}
const headers = {Authorization: `Bearer ${API_TOKEN}`}

// 1. Fetch the initial context and inline it in the system prompt.
async function fetchInitialContext(): Promise<string | null> {
  const url = new URL(MCP_URL!)
  url.pathname = `${url.pathname.replace(/\/$/, '')}/initial-context`
  try {
    const res = await fetch(url, {headers})
    if (!res.ok) throw new Error(`HTTP ${res.status}`)
    return await res.text()
  } catch (err) {
    console.warn(`Could not fetch initial context: ${err}`)
    return null
  }
}

const initialContext = await fetchInitialContext()

let systemPrompt =
  'You are a helpful assistant that answers questions using the Sanity Context tools.'
if (initialContext) {
  systemPrompt += `\n\n# Data reference\n\n${initialContext}`
}

// 2. Connect to the Sanity Context MCP server over Streamable HTTP.
const mcpClient = new MCPAdapter({
  // Keep the server's own tool names (groq_query, not sanity_groq_query).
  prefixToolNameWithServerName: false,
  servers: {
    sanity: {
      transport: 'http',
      url: MCP_URL,
      headers,
    },
  },
})

try {
  // Drop initial_context only if its content is already in the prompt.
  const tools = (await mcpClient.listTools()).filter(
    (t) => !(initialContext && t.name === 'initial_context'),
  )

  // 3. Create the agent and call the model.
  const agent = createAgent({
    model: new ChatAnthropic({model: 'claude-sonnet-5-5'}),
    tools,
    systemPrompt,
  })

  const result = await agent.invoke({
    messages: [{role: 'user', content: process.argv[2] ?? 'What content do we have?'}],
  })
  console.log(result.messages.at(-1)?.text)
} finally {
  await mcpClient.close()
}

A few details differ in LangChain.js:

• MCPAdapter replaces MultiServerMCPClient, which is now a deprecated alias, and listTools() replaces getTools().
• Version 2 of @langchain/mcp-adapters prefixes tool names with the server key by default (sanity_groq_query). The example sets prefixToolNameWithServerName: false so the names match the server's and the initial_context filter works. If you keep the prefix, filter on sanity_initial_context instead.
• If the initial context fetch fails, the TypeScript example logs a warning and keeps the initial_context tool, so the model can still load the schema or outline itself. The Python example stops with an error instead.

Run it with a question. Node.js reads the .env file with --env-file:

node --env-file=.env agent.ts "Do you price match?"

The agent calls the Context MCP tools to explore your content, then prints its answer to the terminal. If the run fails, match the message against the list in Troubleshoot common errors.

createAgent runs on LangGraph, so a LangGraph checkpointer gives the agent memory across turns. @langchain/langgraph is already installed as a dependency of langchain. Add it to your own dependencies, since the example imports it directly:

npm install @langchain/langgraph

pnpm add @langchain/langgraph

yarn add @langchain/langgraph

bun add @langchain/langgraph

Then replace the agent and the invoke call in the try block:

import {MemorySaver} from '@langchain/langgraph'

// ...connect and filter tools as in the full example, then:
const agent = createAgent({
  model: new ChatAnthropic({model: 'claude-sonnet-5-5'}),
  tools,
  systemPrompt,
  // Keeps each conversation's messages, keyed by thread_id
  checkpointer: new MemorySaver(),
})

const config = {configurable: {thread_id: 'support-session-1'}}
for (const question of ['What content do we have?', 'Tell me more about the first one.']) {
  const result = await agent.invoke({messages: [{role: 'user', content: question}]}, config)
  console.log(`> ${question}\n${result.messages.at(-1)?.text}\n`)
}

The second question works because the checkpointer carries the first answer forward on the same thread_id. MemorySaver keeps state in memory; use a persistent checkpointer, such as Postgres, in production.

To use the agent inside a larger graph, add agent.graph as a node, for example new StateGraph(MessagesAnnotation).addNode('sanity', agent.graph). Put the checkpointer on the parent graph, not on the agent.

• [MODULE_TYPELESS_PACKAGE_JSON] Warning: Module type of file:///…/agent.ts is not specified and it doesn't parse as CommonJS.: The agent still runs, but package.json doesn't set the module type. Run npm pkg set type=module. Editors and tsc report the same cause as error TS1309: The current file is a CommonJS module and cannot use 'await' at the top level.
• Error: Set SANITY_CONTEXT_MCP_URL and SANITY_ORGANIZATION_TOKEN: The environment variables aren't loaded. Run with --env-file=.env.
• MCPClientError: Authentication failed for HTTP server "sanity", after Could not fetch initial context: Error: HTTP 401: The token is missing, invalid, or belongs to another organization.
• 403 from the MCP connection with JSON-RPC error -32007 on an endpoint with a dataset source, or -32006 on an endpoint with only Knowledge Base sources, or the same 403 from the /initial-context fetch with code contextGrantRequired or knowledgeBaseAccessDenied. The messages are "Serving a dataset requires an organization API token with Context access ('sanity.knowledge-base.read'). Create one under your organization's API settings in Manage." (dataset source) and "No access to knowledge base '<knowledge base ID>'. Requires one of: sanity.knowledge-base.read." (Knowledge Base sources only; <knowledge base ID> is a placeholder for the Knowledge Base's ID): On an endpoint with a dataset source, the token isn't an organization API token with Context Viewer permissions. On an endpoint with only Knowledge Base sources, the token has no read access to the Knowledge Base the message names. Project tokens are refused however broad their permissions. Create an organization token as described in Prerequisites.
• Error: Anthropic API key not found: Add ANTHROPIC_API_KEY to the .env file. ChatAnthropic throws when it's created, before the agent runs.
• A Zod error about unrecognized_keys from MCPAdapter: The config has an option from version 1, such as useStandardContentBlocks. Remove it.
• Failed to put checkpoint ... missing a required "thread_id": Pass {configurable: {thread_id}} when the agent has a checkpointer.