Permission rules for MCP tools also match another name the tool can go by
Allow and deny rules for MCP tools are now checked against an extra alternative name for each tool, so some deny rules may now apply where they did not
You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
PermissionsArea: what it touches
ImprovementsKind: in v2.1.314,
ImprovementsSection of the release
Unclear It is not stated when a server has a deny alias, so it is unclear how often this changes which rules match.
What
MCP tools are tools provided by outside servers you connect to Claude Code. Your permission rules, the allow and deny lists that decide which tools Claude may use, are checked against a tool's own name and against alternative names for it. Claude Code now builds one more alternative name from the server's deny alias, removes duplicates, and checks your rules against that too. Before, only one alternative name was used.
Why
A deny rule written using the alias name may now block an MCP tool it previously missed. If you rely on such rules, check that they now cover the tools you meant.
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not stated when a server has a deny alias, so it is unclear how often this changes which rules match.
