What
MCP servers are outside programs that give Claude Code extra tools. Claude Code can hold some tools back until they are needed, finding them through tool search. Two things change:
- When a server is marked as deferring all its tools, none of them are loaded up front, even ones that would otherwise always load.
- A tool now counts as safe to run alongside other tools if it is read-only, as before, or if its call is marked as allowed to overlap.
Listing resource templates (patterns describing data a server offers) is now limited to servers that pass a configuration check.
Why
This changes which MCP tools Claude sees from the start and which can run at the same time.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not clear what marks a server as deferring all its tools or a call as allowed to overlap.