{"version":"2.1.321","anchor":"sdk-mcp-servers-pass-an-admission-check-before-connecting","canonical_anchor":"sdk-mcp-servers-pass-an-admission-check-before-connecting","heading":"MCP servers added through the SDK must now pass a check before connecting","tier":"notice","area":"MCP","scope":"both","heads_up":true,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321\/e\/sdk-mcp-servers-pass-an-admission-check-before-connecting","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321","markdown":"### MCP servers added through the SDK must now pass a check before connecting\n\nMCP servers added on the fly through the SDK are checked before and after connecting; a refused one is closed and adds no tools\n\n**Unclear.** What the check compares a server against, such as an organization policy or an allowlist, is not known.\n\n**What**\n\nAn MCP server is an outside program that gives Claude Code extra tools. Programs built on Claude Code's SDK can add such servers while running. These servers used to connect straight away. They are now checked before connecting, after connecting and while their tools are being listed.\n\nIf a server is refused, Claude Code closes it, reports it, and adds none of its tools.\n\n**Why**\n\nRules about which servers are allowed now also cover servers added through the SDK, not only those set up in the usual way.\n\n- Area: MCP\n- Tier: You'll notice\n- Useful: 2\/5\n- Signal: 1\/5\n- Scope: both\n- Heads-up: yes"}