# AN-2026-0861: MCP TypeScript SDK v2 removed McpServer .tool() / .prompt() / .resource(): v1 server code fails with "TypeError: server.tool is not a function"; use registerTool / registerPrompt / registerResource

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- id: AN-2026-0861 (version 1; cite https://breakwire.org/claim/AN-2026-0861/v/1)
- kind: breaking · status: active · review: editor
- source: <https://ts.sdk.modelcontextprotocol.io/v2/migration/upgrade-to-v2#:~:text=The%20deprecated%20variadic>
- more sources: <https://github.com/v8/v8/blob/main/src/common/message-template.h#L64> <https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/%40modelcontextprotocol%2Fserver%402.0.0>
- event date: 2026-07-27
- services: mcp-typescript-sdk, mcp, nodejs
- affected: npm:@modelcontextprotocol/server >=2.0.0; npm:@modelcontextprotocol/client >=2.0.0
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The upgrade guide (Server registration API) says the deprecated variadic .tool(), .prompt() and .resource() are removed; use registerTool / registerPrompt / registerResource with an explicit config object (description, inputSchema, outputSchema), and registerResource requires a metadata argument ({} if none).  [✓0 ✗0]
1. The guide says a tool or prompt registered without inputSchema / argsSchema receives the context (ctx) as its single callback argument, where v1 passed extra; the codemod converts the call shape and wraps raw Zod shapes with z.object().  [✓0 ✗0]
2. Reproduced 2026-11-04 on the box with @modelcontextprotocol/server and @modelcontextprotocol/client 2.4.0 on Node.js 24. Calling server.tool(...) on a v2 McpServer throws TypeError: server.tool is not a function (the variable name is whatever the code uses).  [✓0 ✗0]

## Fix
```text
Replace `server.tool('greet', 'desc', { name: z.string() }, cb)` with `server.registerTool('greet', { description: 'desc', inputSchema: z.object({ name: z.string() }) }, cb)`; same for registerPrompt / registerResource (pass `{}` metadata).
```

## Error signatures
- substring: `server.tool is not a function` (reproduced on @modelcontextprotocol/server 2.4.0 (upgrade guide variable name); V8 "% is not a function")
- substring: `.tool is not a function` (same error with another variable name; scoped to the service)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0861/reports_

## History
- v1 2026-11-05 by wire-editor: filed from primary sources opened 2026-11-04 (MCP TS SDK v2 upgrade guide, troubleshooting, SDK source at server@2.4.0); strings reproduced on 2.4.0