diff --git a/package-lock.json b/package-lock.json
index 3076e2d..d4233e3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "skillcheck",
-  "version": "0.5.0",
+  "version": "0.6.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "skillcheck",
-      "version": "0.5.0",
+      "version": "0.6.0",
       "license": "MIT",
       "dependencies": {
         "commander": "^14.0.3",
diff --git a/src/checks.ts b/src/checks.ts
index e42372c..ff5c384 100644
--- a/src/checks.ts
+++ b/src/checks.ts
@@ -10,6 +10,7 @@ import type {
 
 const MAX_DESCRIPTION_CHARS = 500;
 const COLLISION_THRESHOLD = 0.6;
+const MAX_TOOLS_COUNT = 10;
 
 export function runChecks(
   parsed: ParsedSkill[],
@@ -28,6 +29,7 @@ export function runChecks(
     validated.push(v);
 
     diagnostics.push(...checkTools(v, config));
+    diagnostics.push(...checkToolsOverloaded(v));
     diagnostics.push(...checkDescriptionLength(v));
     diagnostics.push(...checkNameDrift(v));
   }
@@ -94,6 +96,20 @@ function checkTools(v: ValidatedSkill, config: SkillcheckConfig): Diagnostic[] {
   return out;
 }
 
+function checkToolsOverloaded(v: ValidatedSkill): Diagnostic[] {
+  if (v.tools.length >= MAX_TOOLS_COUNT) {
+    return [
+      {
+        severity: "warn",
+        rule: "tools-overloaded",
+        message: `tools: lists ${v.tools.length} tools; narrow the list to the tools this skill actually needs`,
+        file: v.file,
+      },
+    ];
+  }
+  return [];
+}
+
 function checkDescriptionLength(v: ValidatedSkill): Diagnostic[] {
   if (v.description.length > MAX_DESCRIPTION_CHARS) {
     return [
diff --git a/src/sarif.ts b/src/sarif.ts
index a67d02f..328c4d6 100644
--- a/src/sarif.ts
+++ b/src/sarif.ts
@@ -79,7 +79,15 @@ export const RULES: readonly SarifRule[] = [
     id: "description-collision",
     name: "descriptionCollision",
     shortDescription:
-      "Two skills' descriptions overlap on triggers (Jaccard ≥ 0.6).",
+      "Two skills' descriptions overlap on triggers (Jaccard >= 0.6).",
+    helpUri: HELP_BASE,
+    defaultLevel: "warning",
+  },
+  {
+    id: "tools-overloaded",
+    name: "toolsOverloaded",
+    shortDescription:
+      "tools: lists too many entries; listing everything defeats the purpose of the tools filter.",
     helpUri: HELP_BASE,
     defaultLevel: "warning",
   },
diff --git a/test/checks.test.ts b/test/checks.test.ts
index ccb0968..20047aa 100644
--- a/test/checks.test.ts
+++ b/test/checks.test.ts
@@ -167,4 +167,38 @@ describe("runChecks", () => {
     const ds = runChecks([s], config);
     expect(ds.find((d) => d.rule === "name-drift")).toBeUndefined();
   });
+
+  it("warns when tools lists 10 or more entries", () => {
+    const tools = ["Read", "Write", "Edit", "Bash", "Glob", "Grep", "WebFetch", "WebSearch", "TodoWrite", "Agent"];
+    const s = mkSkill("/test/foo/foo.md", {
+      name: "foo",
+      description: "do the foo thing",
+      tools,
+    });
+    const ds = runChecks([s], config);
+    expect(ds.some((d) => d.rule === "tools-overloaded")).toBe(true);
+  });
+
+  it("does not warn when tools lists 9 entries", () => {
+    const tools = ["Read", "Write", "Edit", "Bash", "Glob", "Grep", "WebFetch", "WebSearch", "TodoWrite"];
+    const s = mkSkill("/test/foo/foo.md", {
+      name: "foo",
+      description: "do the foo thing",
+      tools,
+    });
+    const ds = runChecks([s], config);
+    expect(ds.find((d) => d.rule === "tools-overloaded")).toBeUndefined();
+  });
+
+  it("tools-overloaded message includes the count", () => {
+    const tools = ["Read", "Write", "Edit", "Bash", "Glob", "Grep", "WebFetch", "WebSearch", "TodoWrite", "Agent", "ToolSearch"];
+    const s = mkSkill("/test/foo/foo.md", {
+      name: "foo",
+      description: "do the foo thing",
+      tools,
+    });
+    const ds = runChecks([s], config);
+    const d = ds.find((d) => d.rule === "tools-overloaded");
+    expect(d?.message).toContain("11");
+  });
 });