{"version":"2.1.315","anchor":"mcp-tool-list-skip-unchanged-relist-memo-opt-in-by-env-var","canonical_anchor":"mcp-tool-list-skip-unchanged-relist-memo-opt-in-by-env-var","heading":"Opt-in setting to skip rebuilding MCP tool lists that have not changed","tier":"use","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.315\/e\/mcp-tool-list-skip-unchanged-relist-memo-opt-in-by-env-var","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.315","markdown":"### Opt-in setting to skip rebuilding MCP tool lists that have not changed\n\nWith `CLAUDE_CODE_MCP_SKIP_UNCHANGED_RELIST` set to true, Claude Code reuses an MCP server's earlier tool list when nothing changed\n\n**Unclear.** It is not clear whether another condition, besides the environment variable, also has to be met before the remembered list is reused.\n\n**What**\n\nAn MCP server is an outside program that gives Claude Code extra tools. Claude Code asks each server for its list of tools. It now remembers each server's list, along with a fingerprint of the server's configuration and of the tools it returned.\n\nIf you set the environment variable `CLAUDE_CODE_MCP_SKIP_UNCHANGED_RELIST` to exactly `true`, Claude Code reuses the remembered list when nothing has changed within a time window. It does not rebuild the list. An environment variable is a named value you set in your shell before starting Claude Code. Any other value leaves the old behaviour in place.\n\n**Why**\n\nThis saves repeated work fetching and rebuilding MCP tool lists, but only for people who set the variable.\n\n- Area: MCP\n- Tier: Use it now\n- Useful: 4\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: no"}