diff --git a/rust/crates/sift_cli/assets/skills/sift/SKILL.md b/rust/crates/sift_cli/assets/skills/sift/SKILL.md
index 32d21a69e..fc73d0ede 100644
--- a/rust/crates/sift_cli/assets/skills/sift/SKILL.md
+++ b/rust/crates/sift_cli/assets/skills/sift/SKILL.md
@@ -52,6 +52,9 @@ exists.
 - **Report detail:** `list_report_rule_summaries`.
 - **Test results:** `list_test_reports`, `list_test_steps`,
   `list_test_measurements`, `count_test_steps`, `count_test_measurements`.
+  These, along with the `create_test_report` and `append_test_measurements`
+  writes below, are gated behind the `test-reports` Cargo feature (default on).
+  A server built with `--no-default-features` will not expose them.
 - **Data:** `get_data` writes channel data to a Parquet file. `sql` queries
   Parquet files. `upload_dataset` streams a Parquet dataset into Sift.
 - **Links:** `explore_url`.
diff --git a/rust/crates/sift_mcp/CLAUDE.md b/rust/crates/sift_mcp/CLAUDE.md
index c109bbf9a..b6e9fdb55 100644
--- a/rust/crates/sift_mcp/CLAUDE.md
+++ b/rust/crates/sift_mcp/CLAUDE.md
@@ -629,6 +629,30 @@ and `derive_and_upload` are the reference implementations.
 
 ---
 
+## Reference — feature flags
+
+The crate defines Cargo features to let downstream consumers strip individual tool domains from
+the built server. Feature-gated modules follow the same rules as everything else, plus these:
+
+- **`test-reports`** (default on). Gates `service::test_reports`, `tool::test_reports`, the
+  `test_report_service` field and its construction in `server/mod.rs`, the
+  `Self::test_reports_router()` merge, and `UrlService::build_test_report_url`. Building with
+  `--no-default-features` yields a server without the `list_test_reports`, `list_test_steps`,
+  `list_test_measurements`, `count_test_steps`, `count_test_measurements`, `create_test_report`,
+  and `append_test_measurements` tools. All other tools remain available.
+
+When gating a domain behind a feature:
+
+- Wrap every declaration and reference — `pub mod`, `use`, struct field, service construction,
+  router merge, `Self { ... }` init, and any helper on a cross-domain service (see
+  `UrlService::build_test_report_url`) that only that domain calls.
+- Verify both `cargo build -p sift_mcp` and `cargo build -p sift_mcp --no-default-features`
+  build clean, with no dead-code warnings from unused helpers left behind.
+- Update the tool inventory in `rust/crates/sift_cli/assets/skills/sift/SKILL.md` to name the
+  feature next to the affected tools, so agents know why a tool they expected may be missing.
+
+---
+
 ## Pre-merge checklist
 
 Run through this before declaring the tool done:
diff --git a/rust/crates/sift_mcp/Cargo.toml b/rust/crates/sift_mcp/Cargo.toml
index da188dbde..f221a6136 100644
--- a/rust/crates/sift_mcp/Cargo.toml
+++ b/rust/crates/sift_mcp/Cargo.toml
@@ -31,6 +31,9 @@ parquet.workspace = true
 polars = { workspace = true, features = ["lazy", "parquet", "sql"] }
 tokio-stream.workspace = true
 
+[features]
+test-reports = []
+
 [dev-dependencies]
 sift_test_util.workspace = true
 tokio-stream.workspace = true
diff --git a/rust/crates/sift_mcp/src/server/mod.rs b/rust/crates/sift_mcp/src/server/mod.rs
index 3c9569e2a..e4be60508 100644
--- a/rust/crates/sift_mcp/src/server/mod.rs
+++ b/rust/crates/sift_mcp/src/server/mod.rs
@@ -10,11 +10,13 @@ use rmcp::{
 use sift_rs::SiftChannel;
 
 use crate::policy::RetryPolicy;
+#[cfg(feature = "test-reports")]
+use crate::service::test_reports::TestReportService;
 use crate::service::{
     annotations::AnnotationService, assets::AssetService, channels::ChannelService,
     data::DataService, docs::DocsService, ingest::IngestService, ping::PingService,
     report_templates::ReportTemplateService, reports::ReportService, rules::RuleService,
-    runs::RunService, test_reports::TestReportService, url::UrlService, users::UserService,
+    runs::RunService, url::UrlService, users::UserService,
 };
 
 #[derive(Clone)]
@@ -33,6 +35,7 @@ pub struct SiftMcpServer {
     pub report_service: ReportService,
     pub report_template_service: ReportTemplateService,
     pub rule_service: RuleService,
+    #[cfg(feature = "test-reports")]
     pub test_report_service: TestReportService,
     pub docs_service: DocsService,
     pub user_service: UserService,
@@ -93,6 +96,7 @@ impl SiftMcpServer {
         tool_router.merge(Self::ping_router());
         tool_router.merge(Self::rules_router());
         tool_router.merge(Self::annotations_router());
+        #[cfg(feature = "test-reports")]
         tool_router.merge(Self::test_reports_router());
         tool_router.merge(Self::docs_router());
         tool_router.merge(Self::users_router());
@@ -113,6 +117,7 @@ impl SiftMcpServer {
         let report_template_service =
             ReportTemplateService::new(channel.clone(), retry_policy.clone());
         let rule_service = RuleService::new(channel.clone(), retry_policy.clone());
+        #[cfg(feature = "test-reports")]
         let test_report_service = TestReportService::new(channel.clone(), retry_policy.clone());
         let docs_service = DocsService::new(channel.clone(), retry_policy.clone());
         let user_service = UserService::new(channel.clone(), retry_policy);
@@ -129,6 +134,7 @@ impl SiftMcpServer {
             report_service,
             report_template_service,
             rule_service,
+            #[cfg(feature = "test-reports")]
             test_report_service,
             docs_service,
             user_service,
diff --git a/rust/crates/sift_mcp/src/service/mod.rs b/rust/crates/sift_mcp/src/service/mod.rs
index a83451035..2ab197f71 100644
--- a/rust/crates/sift_mcp/src/service/mod.rs
+++ b/rust/crates/sift_mcp/src/service/mod.rs
@@ -9,6 +9,7 @@ pub mod report_templates;
 pub mod reports;
 pub mod rules;
 pub mod runs;
+#[cfg(feature = "test-reports")]
 pub mod test_reports;
 pub mod url;
 pub mod users;
diff --git a/rust/crates/sift_mcp/src/service/url/mod.rs b/rust/crates/sift_mcp/src/service/url/mod.rs
index 595e35311..dd029df5a 100644
--- a/rust/crates/sift_mcp/src/service/url/mod.rs
+++ b/rust/crates/sift_mcp/src/service/url/mod.rs
@@ -127,6 +127,7 @@ impl UrlService {
         Ok(format!("{host}/reports/{}", encode_value(report_id)))
     }
 
+    #[cfg(feature = "test-reports")]
     pub fn build_test_report_url(&self, test_report_id: &str) -> Result<String, ErrorData> {
         let host = self.app_host()?;
         Ok(format!(
diff --git a/rust/crates/sift_mcp/src/tool/mod.rs b/rust/crates/sift_mcp/src/tool/mod.rs
index b82d00e17..199d51416 100644
--- a/rust/crates/sift_mcp/src/tool/mod.rs
+++ b/rust/crates/sift_mcp/src/tool/mod.rs
@@ -10,5 +10,6 @@ pub mod report_templates;
 pub mod reports;
 pub mod rules;
 pub mod runs;
+#[cfg(feature = "test-reports")]
 pub mod test_reports;
 pub mod users;