typescript-sdk/docs/migration-SKILL.md

name	description
migrate-v1-to-v2	Migrate MCP TypeScript SDK code from v1 (@modelcontextprotocol/sdk) to v2 (@modelcontextprotocol/core, /client, /server). Use when a user asks to migrate, upgrade, or port their MCP TypeScript code from v1 to v2.

MCP TypeScript SDK: v1 → v2 Migration

Apply these changes in order: dependencies → imports → API calls → type aliases.

1. Environment

• Node.js 20+ required (v18 dropped)
• ESM only (CJS dropped). If the project uses require(), convert to import/export or use dynamic import().

2. Dependencies

Remove the old package and install only what you need:

npm uninstall @modelcontextprotocol/sdk

You need	Install
Client only	npm install @modelcontextprotocol/client
Server only	npm install @modelcontextprotocol/server
Server + Node.js HTTP	npm install @modelcontextprotocol/server @modelcontextprotocol/node
Server + Express	npm install @modelcontextprotocol/server @modelcontextprotocol/express
Server + Hono	npm install @modelcontextprotocol/server @modelcontextprotocol/hono

@modelcontextprotocol/core is installed automatically as a dependency.

3. Import Mapping

Replace all @modelcontextprotocol/sdk/... imports using this table.

Client imports

v1 import path	v2 package
@modelcontextprotocol/sdk/client/index.js	@modelcontextprotocol/client
@modelcontextprotocol/sdk/client/auth.js	@modelcontextprotocol/client
@modelcontextprotocol/sdk/client/streamableHttp.js	@modelcontextprotocol/client
@modelcontextprotocol/sdk/client/sse.js	@modelcontextprotocol/client
@modelcontextprotocol/sdk/client/stdio.js	@modelcontextprotocol/client
@modelcontextprotocol/sdk/client/websocket.js	@modelcontextprotocol/client

Server imports

v1 import path	v2 package
@modelcontextprotocol/sdk/server/mcp.js	@modelcontextprotocol/server
@modelcontextprotocol/sdk/server/index.js	@modelcontextprotocol/server
@modelcontextprotocol/sdk/server/stdio.js	@modelcontextprotocol/server
@modelcontextprotocol/sdk/server/streamableHttp.js	@modelcontextprotocol/node (class renamed to NodeStreamableHTTPServerTransport)
@modelcontextprotocol/sdk/server/sse.js	REMOVED (migrate to Streamable HTTP)
@modelcontextprotocol/sdk/server/auth/*	REMOVED (use external auth library)
@modelcontextprotocol/sdk/server/middleware.js	@modelcontextprotocol/express (signature changed, see section 8)

Types / shared imports

v1 import path	v2 package
@modelcontextprotocol/sdk/types.js	@modelcontextprotocol/core
@modelcontextprotocol/sdk/shared/protocol.js	@modelcontextprotocol/core
@modelcontextprotocol/sdk/shared/transport.js	@modelcontextprotocol/core
@modelcontextprotocol/sdk/shared/stdio.js	@modelcontextprotocol/core
@modelcontextprotocol/sdk/shared/uriTemplate.js	@modelcontextprotocol/core
@modelcontextprotocol/sdk/shared/auth.js	@modelcontextprotocol/core

Notes:

• @modelcontextprotocol/client and @modelcontextprotocol/server both re-export everything from @modelcontextprotocol/core, so you can import types from whichever package you already depend on.
• When multiple v1 imports map to the same v2 package, consolidate them into a single import statement.
• If code imports from sdk/client/..., install @modelcontextprotocol/client. If from sdk/server/..., install @modelcontextprotocol/server. If from sdk/types.js or sdk/shared/... only, install @modelcontextprotocol/core.

4. Renamed Symbols

v1 symbol	v2 symbol	v2 package
StreamableHTTPServerTransport	NodeStreamableHTTPServerTransport	@modelcontextprotocol/node

5. Removed / Renamed Type Aliases and Symbols

v1 (removed)	v2 (replacement)
JSONRPCError	JSONRPCErrorResponse
JSONRPCErrorSchema	JSONRPCErrorResponseSchema
isJSONRPCError	isJSONRPCErrorResponse
isJSONRPCResponse	isJSONRPCResultResponse
ResourceReference	ResourceTemplateReference
ResourceReferenceSchema	ResourceTemplateReferenceSchema
IsomorphicHeaders	REMOVED (use Web Standard Headers)
AuthInfo (from server/auth/types.js)	AuthInfo (now in @modelcontextprotocol/core)

All other symbols from @modelcontextprotocol/sdk/types.js retain their original names (e.g., CallToolResultSchema, ListToolsResultSchema, etc.).

Unchanged APIs (only import paths changed): Client constructor and methods, McpServer constructor, server.connect(), server.close(), all client transports (StreamableHTTPClientTransport, SSEClientTransport, StdioClientTransport), StdioServerTransport, all Zod schemas, all callback return types.

6. McpServer API Changes

The variadic .tool(), .prompt(), .resource() methods are removed. Use the register* methods with a config object.

Tools

// v1: server.tool(name, schema, callback)
server.tool('greet', { name: z.string() }, async ({ name }) => {
  return { content: [{ type: 'text', text: `Hello, ${name}!` }] };
});

// v1: server.tool(name, description, schema, callback)
server.tool('greet', 'Greet a user', { name: z.string() }, async ({ name }) => {
  return { content: [{ type: 'text', text: `Hello, ${name}!` }] };
});

// v2: server.registerTool(name, config, callback)
server.registerTool('greet', {
  description: 'Greet a user',
  inputSchema: { name: z.string() },
}, async ({ name }) => {
  return { content: [{ type: 'text', text: `Hello, ${name}!` }] };
});

Config object fields: title?, description?, inputSchema?, outputSchema?, annotations?, _meta?

Prompts

// v1: server.prompt(name, schema, callback)
server.prompt('summarize', { text: z.string() }, async ({ text }) => {
  return { messages: [{ role: 'user', content: { type: 'text', text } }] };
});

// v2: server.registerPrompt(name, config, callback)
server.registerPrompt('summarize', {
  argsSchema: { text: z.string() },
}, async ({ text }) => {
  return { messages: [{ role: 'user', content: { type: 'text', text } }] };
});

Config object fields: title?, description?, argsSchema?

Resources

// v1: server.resource(name, uri, callback)
server.resource('config', 'config://app', async (uri) => {
  return { contents: [{ uri: uri.href, text: '{}' }] };
});

// v2: server.registerResource(name, uri, metadata, callback)
server.registerResource('config', 'config://app', {}, async (uri) => {
  return { contents: [{ uri: uri.href, text: '{}' }] };
});

Note: the third argument (metadata) is required — pass {} if no metadata.

7. Headers API

Transport constructors and RequestInfo.headers now use the Web Standard Headers object instead of plain objects.

// v1: plain object, bracket access
headers: { 'Authorization': 'Bearer token' }
extra.requestInfo?.headers['mcp-session-id']

// v2: Headers object, .get() access
headers: new Headers({ 'Authorization': 'Bearer token' })
extra.requestInfo?.headers.get('mcp-session-id')

8. Removed Server Features

SSE server transport

SSEServerTransport removed entirely. Migrate to NodeStreamableHTTPServerTransport (from @modelcontextprotocol/node). Client-side SSEClientTransport still available for connecting to legacy servers.

Server-side auth

All server OAuth exports removed: mcpAuthRouter, OAuthServerProvider, OAuthTokenVerifier, requireBearerAuth, authenticateClient, ProxyOAuthServerProvider, allowedMethods, and associated types. Use an external auth library (e.g., better-auth). See examples/server/src/ for demos.

Host header validation (Express)

hostHeaderValidation() and localhostHostValidation() moved from server package to @modelcontextprotocol/express. Signature changed: takes string[] instead of options object.

// v1
import { hostHeaderValidation } from '@modelcontextprotocol/sdk/server/middleware.js';
app.use(hostHeaderValidation({ allowedHosts: ['example.com'] }));

// v2
import { hostHeaderValidation } from '@modelcontextprotocol/express';
app.use(hostHeaderValidation(['example.com']));

The server package now exports framework-agnostic alternatives: validateHostHeader(), localhostAllowedHostnames(), hostHeaderValidationResponse().

9. Client Behavioral Changes

Client.listPrompts(), listResources(), listResourceTemplates(), listTools() now return empty results when the server lacks the corresponding capability (instead of sending the request). Set enforceStrictCapabilities: true in ClientOptions to throw an error instead.

10. Migration Steps (apply in this order)

1. Update package.json: npm uninstall @modelcontextprotocol/sdk, install the appropriate v2 packages
2. Replace all imports from @modelcontextprotocol/sdk/... using the import mapping tables (sections 3-4), including StreamableHTTPServerTransport → NodeStreamableHTTPServerTransport
3. Replace removed type aliases (JSONRPCError → JSONRPCErrorResponse, etc.) per section 5
4. Replace .tool() / .prompt() / .resource() calls with registerTool / registerPrompt / registerResource per section 6
5. Replace plain header objects with new Headers({...}) and bracket access (headers['x']) with .get() calls per section 7
6. If using hostHeaderValidation from server, update import and signature per section 8
7. If using server SSE transport, migrate to Streamable HTTP
8. If using server auth from the SDK, migrate to an external auth library
9. If relying on listTools()/listPrompts()/etc. throwing on missing capabilities, set enforceStrictCapabilities: true
10. Verify: build with tsc / run tests