{"version":"2.1.321","anchor":"files-extension-upload-validation-for-mcp-tasks","canonical_anchor":"files-extension-upload-validation-for-mcp-tasks","heading":"File upload requests from MCP servers are checked before they are accepted","tier":"notice","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321\/e\/files-extension-upload-validation-for-mcp-tasks","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.321","markdown":"### File upload requests from MCP servers are checked before they are accepted\n\nClaude Code checks file upload requests from MCP servers and rejects ones that are malformed\n\n**What**\n\nMCP servers are add-ons that give Claude extra tools, and some can ask Claude Code to upload files to them. Claude Code now checks those upload requests against a set of rules and rejects ones that are malformed. The rules cover the request's list of uploads and files, the upload method `io.modelcontextprotocol\/files\/upload`, and upload targets, which must accept a PUT request.\n\n**Why**\n\nThis is part of Claude Code's support for the MCP files extension, the part of the protocol that lets servers ask for file uploads.\n\n- Area: MCP\n- Tier: You'll notice\n- Useful: 2\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: no"}