You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.323,
ImprovementsSection of the release
What
An MCP tool is a tool from an outside program you connected. Each tool describes the arguments it takes. Claude Code looks through that description for arguments that are files and changes how they are shown to Claude.
Before, it only recognised a single file, an optional file, or a list of files. It now also handles:
Arguments that can take one of several forms
Forms that allow an empty value
File entries given only by a fingerprint, with no file name
The parts it recognises are hidden or listed, and the argument's description is rewritten. Claude Code works this out once per tool definition and reuses it.
Why
For MCP tools with these more complex argument descriptions, file arguments now look different to Claude.
