{"version":"2.1.321","anchor":"mcp-set-servers-can-deny-tools-and-reconnect-needs-auth-serv","canonical_anchor":"mcp-set-servers-can-deny-tools-and-reconnect-needs-auth-serv","heading":"Programs driving Claude Code can now deny tools and reconnect servers awaiting sign-in","tier":"use","area":"SDK","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321\/e\/mcp-set-servers-can-deny-tools-and-reconnect-needs-auth-serv","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321","markdown":"### Programs driving Claude Code can now deny tools and reconnect servers awaiting sign-in\n\nUpdating MCP servers from a program can now include tools to deny, and servers waiting for sign-in are retried afterwards\n\n**Unclear.** The retry of servers waiting for sign-in sits behind a check whose setting is not known, so it may not run for every session.\n\n**What**\n\nMCP servers are add-ons that give Claude extra tools. A program that drives Claude Code through the SDK (the developer kit for controlling Claude Code from code) or from a remote host can replace the list of MCP servers with a single `mcp_set_servers` request. That request changed in these ways:\n\n- `deniedTools`: a new option listing tools Claude may not use. These denials are added to the permission rules for the session.\n\n- Servers waiting for sign-in: after the list is replaced, any server the request names that is in the \"needs authentication\" state is tried again. If it still cannot connect, Claude Code logs \"Could not connect after mcp_set_servers\".\n\n- SDK server settings: these can now carry a list of tools tied to automatic permission decisions.\n\n- Always-deny rules: certain held-back artifact entries are now checked against your always-deny rules before they are used.\n\n**Why**\n\nA host program can block tools and get stalled servers connected again without restarting Claude Code.\n\n- Area: SDK\n- Names: `mcp_set_servers`\n- Tier: Use it now\n- Useful: 4\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: no"}