{"version":"2.1.319","anchor":"mcp-tool-call-error-handler-nohandler-path","canonical_anchor":"mcp-tool-call-error-handler-nohandler-path","heading":"MCP tool errors can now be raised with a message written for Claude","tier":"internal","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.319\/e\/mcp-tool-call-error-handler-nohandler-path","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.319","markdown":"### MCP tool errors can now be raised with a message written for Claude\n\nWhen an MCP tool call fails and no handler deals with the error, Claude Code now raises an error carrying the message meant for Claude\n\n**What**\n\nMCP (Model Context Protocol) is the way Claude Code connects to outside tools and services. When a tool call to one of these fails, Claude Code sorts the error into a category. There is now an extra step after that: if the category comes with a message written for Claude and has no handler to deal with it, Claude Code raises an error that carries that message. Otherwise the handler runs as before.\n\n**Why**\n\nThis is a new route by which an MCP tool failure can be reported back to Claude.\n\n- Area: MCP\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 1\/5\n- Scope: individual\n- Heads-up: no"}