MCP clients can now send scope on OAuth refresh, which unblocks servers behind Microsoft Entra ID. The release also adds a Skills client that verifies size, digest, and SKILL.md frontmatter.
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 → client 2.4.0 adds opt-in scope on OAuth refresh via OAuthClientProvider.scopeForRefresh(tokenThe chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.Full definition →), for Microsoft Entra ID, which returns AADSTS90009 on a scopeless refresh when client and resource share one app registration.
Without the new option, refresh requests and saved tokens are unchanged. When a scope is sent and the token response has none, the sent scope is kept on the returned tokens.
SkillsClient.list() throws on an invalid entry unless skipInvalid: true, which returns valid skills plus an invalid list. read() checks size, digest and 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 → frontmatter, refetching a failed cached copy once before raising SkillVerificationError.
The client also bundles fast-uri 3.1.8, so tools whose schema $id or $ref uses an invalid URI scheme, such as my_tool:output, now fail with an invalid-schema error.
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 hook — A script the harness runs automatically at a fixed point in an agent's loop — before a tool call, after an edit, on session start.
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.
token — The chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.
