You'll notice
Useful3 Signal3
Names you or a caller supply are sanitised before appearing in error messages.
What's wrong with this entry?
Anonymous. No account, no email.
/mcp
What
Names and actions that you type or that arrive from a caller are now passed through a sanitiser before being placed into the error text sent back, instead of being embedded raw. This covers the inline /mcp command and the rejection messages for event submissions, so a crafted name cannot inject its own content into the message you or a client sees.
Details
/mcpsanitises both the action and the server name you typed when building its unrecognised-action message and its unknown-server message, the latter readingThere's no MCP server named ".- The action
/mcprecords in telemetry is sanitised the same way, not just the action shown on screen. - Event submissions refused for using a reserved name, with text noting the name
is reserved for a server-authored producer, and those refused for a name mismatch, both sanitise the caller-supplied name before it reaches the error string. - The remaining checks on event submissions are untouched: the cap on envelope size, the accepted authority values, and the provenance check on sender text all behave as before.
Evidence
There's no MCP server named ", is reserved for a server-authored producer
Strings lifted out of the shipped bundle, so the claim above can be checked against them.