MCP servers can now serve AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → skills through a standard extension, with invalid skills skipped or failed in strict mode. Gateways can forward change notifications with their metadata.
Key takeaways · AI-distilled
MCPThe Model Context Protocol — an open standard that lets any AI assistant plug into any tool or data source without custom integration code.Full definition → TypeScript SDK 2.4.0 adds the Skills extension (SEP-2640) under new ext/skills subpaths: SkillsExtension.attach(server) serves skills/list, skills/get and a agent skillA reusable instruction file that teaches an agent how to do one job well — the procedure, the tools, and what counts as done.Full definition →:// resource template. attach is marked experimental; the rest of the Skills API is stable.
The bundled Ajv validator now uses fast-uri 3.1.8, so a schema whose $id or $ref has an invalid URI scheme, such as my_tool:output, no longer compiles and the tool fails with an invalid-schema error. Names like my_tool_output are unaffected.
x-mcp-header on a number-typed tool parameter is now rejected, per the 2026-07-28 spec, and clients on non-stdio 2026-07-28 connections no longer list such tools. Using an integer type (z.int()) or removing the annotation resolves it.
A tool outputSchema whose root is a $ref to an object definition is now treated as an object schema, so 2025-era clients that read structuredContent.result for such a tool must read structuredContent instead.
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.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
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.
