diff --git a/ast-grep-rule-tests/no-expand-top-level-tools-test.yml b/ast-grep-rule-tests/no-expand-top-level-tools-test.yml
new file mode 100644
index 000000000..ae175cb89
--- /dev/null
+++ b/ast-grep-rule-tests/no-expand-top-level-tools-test.yml
@@ -0,0 +1,55 @@
+id: no-expand-top-level-tools
+valid:
+  - |
+    export const TOP_LEVEL_TOOL_NAMES = [
+      "find_organizations",
+      "find_projects",
+      "update_issue",
+      "search_errors",
+      "search_logs",
+      "search_traces",
+      "search_metrics",
+      "search_profiles",
+      "search_replays",
+      "analyze_issue_with_seer",
+      "search_issues",
+      "get_sentry_resource",
+      ...CATALOG_INFRASTRUCTURE_TOOL_NAMES,
+    ] as const;
+  - |
+    export const EXPERIMENTAL_TOP_LEVEL_TOOL_NAMES = TOP_LEVEL_TOOL_NAMES;
+invalid:
+  - |
+    export const TOP_LEVEL_TOOL_NAMES = [
+      "find_organizations",
+      "find_projects",
+      "update_issue",
+      "search_errors",
+      "search_logs",
+      "search_traces",
+      "search_metrics",
+      "search_profiles",
+      "search_replays",
+      "find_dropped_events",
+      "analyze_issue_with_seer",
+      "search_issues",
+      "get_sentry_resource",
+      ...CATALOG_INFRASTRUCTURE_TOOL_NAMES,
+    ] as const;
+  - |
+    export const TOP_LEVEL_TOOL_NAMES = [
+      "find_organizations",
+      "find_projects",
+      "update_issue",
+      "search_errors",
+      "search_logs",
+      "search_traces",
+      "search_metrics",
+      "search_profiles",
+      "search_replays",
+      "analyze_issue_with_seer",
+      "search_issues",
+      "get_sentry_resource",
+      ...CATALOG_INFRASTRUCTURE_TOOL_NAMES,
+      ...EXTRA_TOOL_NAMES,
+    ] as const;
diff --git a/ast-grep-rules/no-expand-top-level-tools.yml b/ast-grep-rules/no-expand-top-level-tools.yml
new file mode 100644
index 000000000..565399dac
--- /dev/null
+++ b/ast-grep-rules/no-expand-top-level-tools.yml
@@ -0,0 +1,39 @@
+id: no-expand-top-level-tools
+language: TypeScript
+severity: error
+message: Do not change the default top-level MCP tool list.
+note: |
+  Every tool in TOP_LEVEL_TOOL_NAMES ships in the default tools/list payload.
+  Many harnesses still load every listed tool definition into the context
+  window up front, so each addition is noise for every session. Keep new tools
+  deferred: they stay reachable through search_sentry_tools and
+  execute_sentry_tool. Restricted until tool search is standard in every
+  mainstream harness, which likely happens by 2027. If the list truly must
+  change, update the allowed list in this rule in the same PR so the change is
+  reviewed explicitly.
+rule:
+  kind: lexical_declaration
+  has:
+    kind: variable_declarator
+    has:
+      field: name
+      regex: ^TOP_LEVEL_TOOL_NAMES$
+  not:
+    pattern: |
+      const TOP_LEVEL_TOOL_NAMES = [
+        "find_organizations",
+        "find_projects",
+        "update_issue",
+        "search_errors",
+        "search_logs",
+        "search_traces",
+        "search_metrics",
+        "search_profiles",
+        "search_replays",
+        "analyze_issue_with_seer",
+        "search_issues",
+        "get_sentry_resource",
+        ...CATALOG_INFRASTRUCTURE_TOOL_NAMES
+      ] as const
+files:
+  - packages/mcp-core/src/tools/surfaces.ts
diff --git a/packages/mcp-core/src/server.test.ts b/packages/mcp-core/src/server.test.ts
index 3b685213a..d0a99a772 100644
--- a/packages/mcp-core/src/server.test.ts
+++ b/packages/mcp-core/src/server.test.ts
@@ -119,7 +119,6 @@ async function callRegisteredTool(
 const DEFAULT_DIRECT_TOOL_NAMES = [
   "analyze_issue_with_seer",
   "execute_sentry_tool",
-  "find_dropped_events",
   "find_organizations",
   "find_projects",
   "get_sentry_resource",
diff --git a/packages/mcp-core/src/toolDefinitions.json b/packages/mcp-core/src/toolDefinitions.json
index 14cdea45f..3165f01c0 100644
--- a/packages/mcp-core/src/toolDefinitions.json
+++ b/packages/mcp-core/src/toolDefinitions.json
@@ -2187,7 +2187,7 @@
     },
     "requiredScopes": ["event:read"],
     "skills": ["inspect"],
-    "surface": "direct"
+    "surface": "catalog"
   },
   {
     "name": "find_dsns",
diff --git a/packages/mcp-core/src/tools/surfaces.ts b/packages/mcp-core/src/tools/surfaces.ts
index b5f6d89e6..755f60ea6 100644
--- a/packages/mcp-core/src/tools/surfaces.ts
+++ b/packages/mcp-core/src/tools/surfaces.ts
@@ -14,6 +14,11 @@ export const CATALOG_INFRASTRUCTURE_TOOL_NAMES = [
 
 export const WRAPPER_TOOL_NAMES = [] as const;
 
+// Locked by ast-grep-rules/no-expand-top-level-tools.yml. Every name here ships
+// in the default tools/list payload, and many harnesses still load every listed
+// tool into the context window up front. New tools stay deferred behind
+// search_sentry_tools/execute_sentry_tool. Restricted until tool search is
+// standard in every mainstream harness, which likely happens by 2027.
 export const TOP_LEVEL_TOOL_NAMES = [
   "find_organizations",
   "find_projects",
@@ -24,7 +29,6 @@ export const TOP_LEVEL_TOOL_NAMES = [
   "search_metrics",
   "search_profiles",
   "search_replays",
-  "find_dropped_events",
   "analyze_issue_with_seer",
   "search_issues",
   "get_sentry_resource",
diff --git a/plugins/sentry-mcp-experimental/agents/sentry-mcp.md b/plugins/sentry-mcp-experimental/agents/sentry-mcp.md
index eebfb87b7..37705a4f0 100644
--- a/plugins/sentry-mcp-experimental/agents/sentry-mcp.md
+++ b/plugins/sentry-mcp-experimental/agents/sentry-mcp.md
@@ -12,7 +12,6 @@ mcpServers:
 allowedTools:
   - analyze_issue_with_seer
   - execute_sentry_tool
-  - find_dropped_events
   - find_organizations
   - find_projects
   - get_sentry_resource
diff --git a/plugins/sentry-mcp/agents/sentry-mcp.md b/plugins/sentry-mcp/agents/sentry-mcp.md
index eebfb87b7..37705a4f0 100644
--- a/plugins/sentry-mcp/agents/sentry-mcp.md
+++ b/plugins/sentry-mcp/agents/sentry-mcp.md
@@ -12,7 +12,6 @@ mcpServers:
 allowedTools:
   - analyze_issue_with_seer
   - execute_sentry_tool
-  - find_dropped_events
   - find_organizations
   - find_projects
   - get_sentry_resource