feat(router): support runtime disabling of tools#809
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lutz-grex wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
feat(router): support runtime disabling of tools#809lutz-grex wants to merge 1 commit intomodelcontextprotocol:mainfrom
lutz-grex wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Add methods to disable/enable tools at runtime. Disabled tools are hidden from listing, lookup, and execution, including in composed routers. Closes modelcontextprotocol#477
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DaleSeo
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@lutz-grex How should clients learn about runtime disable/enable? I'm worried that the list_tools results will go stale until the client re-lists. I believe the MCP spec has notifications/tools/list_changed for this.
https://modelcontextprotocol.io/specification/2025-11-25/server/tools#list-changed-notification
| /// Returns `true` if the tool exists in the router but is currently | ||
| /// disabled. | ||
| pub fn is_disabled(&self, name: &str) -> bool { | ||
| self.map.contains_key(name) && self.disabled.contains(name) |
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What happens if a tool is disabled before it's added? Is this supposed to return false?
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| pub fn disable_route(&mut self, name: &str) { | ||
| self.disabled.insert(Cow::Owned(name.to_owned())); |
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with_disabled accepts impl Into<Cow<'static, str>>, but disable_route accepts &str. Can we align these two APIs so that callers don't have to choose between builder and mutable styles based on how memory is allocated?
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Add methods to disable/enable tools at runtime.
Disabled tools are hidden from listing, lookup,
and execution, including in composed routers.
Closes #477
Motivation and Context
Users of the
#[tool]+#[tool_handler]macro system had no way to disable specific tools at runtime. The only workaround was manually implementingServerHandler, losing all macro convenience, or usingremove_routewhich permanently destroys the tool.This change adds reversible disable/enable support directly to
ToolRouter, composing naturally with the existing macro workflow:How Has This Been Tested?
test_tool_routers.rscovering:disable, enable, builder pattern, merge preservation,
remove cleanup, pre-disable before add, iterator
filtering, and full invisibility across all query methods
cargo test -p rmcp)disable_routeandenable_routedo not compile on the baseline and workcorrectly after the change
cargo clippy --all-targets --all-featurescleancargo +nightly fmt --allcleanBreaking Changes
has_routenow returnsfalsefor disabled tools (previouslyit only checked map membership). Code relying on
has_routeto test structural presence regardless of enabled state should
use
is_disabledinstead. TheToolRouterstruct is#[non_exhaustive], so adding the privatedisabledfield isnot a breaking change.
Types of changes
Checklist
Additional context
Three files changed:
crates/rmcp/src/handler/server/router/tool.rs— corefeature:
disabledHashSet field, disable/enable/is_disabled/with_disabled methods, updated list_all/call/get/has_route
/merge/remove_route/IntoIterator
crates/rmcp/src/handler/server/router.rs— one-line fix:transparent_when_not_founddispatch now checksis_disabledso disabled tools cannot leak through to the inner service
crates/rmcp/tests/test_tool_routers.rs— 9 new tests