Intel / repo

typescript-sdk v2.4.0 — 2.4.0

Source: github.com
Author: felixweinberger
Date: Published Oct 23, 2026

From the Daily Brief

The MCP TypeScript SDK 2.4.0 implements the Skills extension, SEP-2640, one day after Anthropic handed the Agent Skills format to the foundation that runs MCP. On the server side, SkillsExtension answers skills/list and skills/get, loads skills from a folder and validates them, skipping invalid ones or failing in strict mode. On the client side, a SkillsClient lists skills and verifies their integrity. That turns yesterday's governance change into something developers can ship: a server can now publish skills over the protocol instead of each platform reading SKILL.md files from disk. The release also adds an opt-in scopeForRefresh hook for authorization servers like Microsoft Entra ID that reject refresh requests without a scope. Its upgrade notes list behavior changes that break existing tools, including rejection of number-typed x-mcp-header and outputSchema results no longer wrapped in a result key.

Read the 2026-10-24 Brief →

Key takeaways · AI-distilled

In TypeScript SDK 2.4.0, a tool that puts x-mcp-header on a number parameter fails on both sides: the client leaves it out of the tool list and the server answers calls with error -32020. The notes say to use z.int() or drop the annotation.
On 2025-11-25 connections, an outputSchema built from z.object(...).meta({ id }) no longer wraps results in { result }, so clients have to read structuredContent directly rather than structuredContent.result.
The bundled Ajv validator now uses fast-uri 3.1.8, which rejects a $id or $ref with an invalid URI scheme such as my_tool:output, so schemas named that way are refused after the upgrade.
Skills over MCP (SEP-2640) works on both the 2025-11-25 and 2026-07-28 protocol revisions, but the release marks skills.attach as experimental and says it may change in a minor release.

Terms in this piece · Glossary

MCP — The Model Context Protocol — an open standard that lets any AI assistant plug into any tool or data source without custom integration code.
agent skill — A reusable instruction file that teaches an agent how to do one job well — the procedure, the tools, and what counts as done.

Read the source github.com