{"version":"2.1.311","anchor":"mcp-tool-results-with-structuredcontent-that-fail-a-check-no","canonical_anchor":"mcp-tool-results-with-structuredcontent-that-fail-a-check-no","heading":"Some MCP tool results now fail with an error naming the server and tool","tier":"notice","area":"MCP","scope":"individual","heads_up":true,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.311\/e\/mcp-tool-results-with-structuredcontent-that-fail-a-check-no","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.311","markdown":"### Some MCP tool results now fail with an error naming the server and tool\n\nAfter an MCP tool call, Claude Code now runs a new check on the tool's structured result and raises an error naming the server and tool if it fails\n\n**Unclear.** It is not clear what the new check looks for in structuredContent, so which results now cause an error is unknown.\n\n**What**\n\nMCP servers are outside programs that give Claude Code extra tools. Some of them return `structuredContent`, which is result data in a fixed shape. After an MCP tool call, Claude Code now runs a new check on that data. When the check fails, the call ends in an error that names the MCP server and the tool. Before, there was no such check.\n\n**Why**\n\nSome MCP tool calls that used to return a result may now stop with an error instead. The error names the server and the tool, so you can tell which one to look at.\n\n- Area: MCP\n- Tier: You'll notice\n- Useful: 2\/5\n- Signal: 1\/5\n- Scope: individual\n- Heads-up: yes"}