diff --git a/cookbook/snippets/assembly-connector-and-revolute-mate.md b/cookbook/snippets/assembly-connector-and-revolute-mate.md
new file mode 100644
index 000000000..0825719c6
--- /dev/null
+++ b/cookbook/snippets/assembly-connector-and-revolute-mate.md
@@ -0,0 +1,36 @@
+---
+id: assembly-connector-and-revolute-mate
+title: Declare a connector and join parts with a revolute mate
+tags: [assembly, connector, mate, revolute, hinge, joint]
+keywords:
+  - assembly with parts connectors and mates
+  - how do I declare a connector
+  - revolute joint
+  - hinge
+  - axis connector origin
+  - pivot joint between parts
+  - declare connector and mate
+when_to_use: >-
+  The model has multiple mechanical parts (not a single fused body) that
+  need a named pivot between them. Declare an axis connector on each part
+  with partRef.connector(name, { type: 'axis', origin: { kind: 'vec3', value:
+  [...] }, axis: [...] }), then join the connectors with arm.mate(name,
+  'partA.conn', 'partB.conn', 'revolute', { limitsDeg: [min, max] }). This is
+  the canonical assembly-topology vocabulary for hinges, elbows, and any
+  revolute joint — connector origins must use the tagged
+  { kind: 'vec3', value: [...] } form, not a bare [x, y, z] array.
+---
+
+```typescript
+const arm = assembly('two-link-arm');
+
+const base = arm.part('base', box(40, 40, 16));
+const link = arm.part('arm', box(10, 40, 6).translate(0, 20, 0));
+
+base.connector('pivot', { type: 'axis', origin: { kind: 'vec3', value: [5, 20, 16] }, axis: [0, 1, 0] });
+link.connector('pivot', { type: 'axis', origin: { kind: 'vec3', value: [0, 0, 0] }, axis: [0, 1, 0] });
+
+arm.mate('elbow', 'base.pivot', 'arm.pivot', 'revolute', { limitsDeg: [0, 90] });
+
+return arm.solvedModel({ elbow: 45 });
+```
diff --git a/cookbook/snippets/clamshell-hinge-two-part-assembly.md b/cookbook/snippets/clamshell-hinge-two-part-assembly.md
new file mode 100644
index 000000000..12ea9dffc
--- /dev/null
+++ b/cookbook/snippets/clamshell-hinge-two-part-assembly.md
@@ -0,0 +1,34 @@
+---
+id: clamshell-hinge-two-part-assembly
+title: Clamshell hinge between a base and a lid, joined by a revolute mate
+tags: [assembly, connector, mate, revolute, hinge, joint]
+keywords:
+  - hinge
+  - revolute joint
+  - clamshell hinge
+  - lid pivots on base
+  - assembly with connectors and mates
+  - declare a connector
+  - hingeAxis connector
+when_to_use: >-
+  You are modeling a laptop-lid-style clamshell hinge, or any assembly
+  where one rigid body swings about a fixed pivot line on another rigid
+  body. Declare a matching axis connector on both bodies along the
+  physical hinge line, then join them with a revolute mate and limitsDeg
+  to bound the swing angle. Relevant for hinge, revolute joint, or
+  assembly with connectors and mates.
+---
+
+```typescript
+const arm = assembly('clamshell-hinge');
+
+const base = arm.part('base', box(300, 200, 12).translate(0, 0, 6));
+const lid = arm.part('lid', box(300, 200, 6).translate(0, 100, 3));
+
+base.connector('hingeAxis', { type: 'axis', origin: { kind: 'vec3', value: [0, -100, 12] }, axis: [1, 0, 0] });
+lid.connector('hingeAxis', { type: 'axis', origin: { kind: 'vec3', value: [0, 0, 0] }, axis: [1, 0, 0] });
+
+arm.mate('hinge', 'base.hingeAxis', 'lid.hingeAxis', 'revolute', { limitsDeg: [-15, 135] });
+
+return arm.solvedModel({ hinge: 90 });
+```
diff --git a/cookbook/tags.json b/cookbook/tags.json
index 9dd24a90b..d6833f0c4 100644
--- a/cookbook/tags.json
+++ b/cookbook/tags.json
@@ -23,5 +23,11 @@
   "joinery",
   "bracket",
   "stacking",
-  "symmetry"
+  "symmetry",
+  "assembly",
+  "connector",
+  "mate",
+  "revolute",
+  "hinge",
+  "joint"
 ]
diff --git a/src/agent/mcp/tools/mechanismCookbook.test.ts b/src/agent/mcp/tools/mechanismCookbook.test.ts
new file mode 100644
index 000000000..88d533e6c
--- /dev/null
+++ b/src/agent/mcp/tools/mechanismCookbook.test.ts
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 Andrii Shylenko and kernelCAD contributors
+//
+// KC-10: lookup_cookbook could not see any mechanism/assembly content — every
+// query about connectors, mates, or hinges returned single-body geometry
+// snippets (top hit for "assembly with parts, connectors and mates" was
+// mirror-half-part). This asserts the cookbook corpus now surfaces the
+// mechanism snippets for the queries that used to fall through to
+// single-body geometry.
+import { describe, it, expect } from 'vitest';
+import { lookupCookbookTool } from './lookupCookbook';
+
+const MECHANISM_SNIPPET_IDS = new Set([
+  'assembly-connector-and-revolute-mate',
+  'clamshell-hinge-two-part-assembly',
+]);
+
+describe('lookupCookbookTool — mechanism/assembly coverage (KC-10)', () => {
+  const queries = [
+    'assembly with parts connectors and mates',
+    'hinge',
+    'revolute joint',
+    'how do I declare a connector',
+  ];
+
+  for (const query of queries) {
+    it(`returns a mechanism snippet for "${query}"`, async () => {
+      const r = await lookupCookbookTool({ query });
+      expect(r.ok).toBe(true);
+      expect(r.hits!.length).toBeGreaterThan(0);
+      const ids = r.hits!.map((h) => h.id);
+      expect(ids.some((id) => MECHANISM_SNIPPET_IDS.has(id))).toBe(true);
+    });
+  }
+
+  it('the returned mechanism snippet shows the tagged connector-origin form, not a bare array', async () => {
+    const r = await lookupCookbookTool({ query: 'how do I declare a connector' });
+    const hit = r.hits!.find((h) => MECHANISM_SNIPPET_IDS.has(h.id));
+    expect(hit).toBeDefined();
+    expect(hit!.body).toContain("origin: { kind: 'vec3', value:");
+    expect(hit!.body).toMatch(/type: 'axis'/);
+    expect(hit!.body).toMatch(/'revolute'/);
+  });
+});
diff --git a/src/agent/skills/kernelcad-authoring/SKILL.md b/src/agent/skills/kernelcad-authoring/SKILL.md
index 94be2ea4c..420c1d7a0 100644
--- a/src/agent/skills/kernelcad-authoring/SKILL.md
+++ b/src/agent/skills/kernelcad-authoring/SKILL.md
@@ -828,8 +828,10 @@ When you need a canonical pattern, call MCP tool `lookup_cookbook(query, k?)` to
 
 | ID | Trigger |
 |---|---|
+| assembly-connector-and-revolute-mate | The model has multiple mechanical parts (not a single fused body) that need a named pivot between them. Declare an axis connector on each part with partRef.connector(name, { type: 'axis', origin: { kind: 'vec3', value: [...] }, axis: [...] }), then join the connectors with arm.mate(name, 'partA.conn', 'partB.conn', 'revolute', { limitsDeg: [min, max] }). This is the canonical assembly-topology vocabulary for hinges, elbows, and any revolute joint — connector origins must use the tagged { kind: 'vec3', value: [...] } form, not a bare [x, y, z] array. |
 | blind-pocket-from-top | You want a pocket cut into the top face only — the cylinder is shorter than the plate so it does not reach the bottom face. |
 | chamfer-rotated-face | You rotated a primitive and now want to chamfer one of its canonical faces by name (face-name semantics survive transforms). |
+| clamshell-hinge-two-part-assembly | You are modeling a laptop-lid-style clamshell hinge, or any assembly where one rigid body swings about a fixed pivot line on another rigid body. Declare a matching axis connector on both bodies along the physical hinge line, then join them with a revolute mate and limitsDeg to bound the swing angle. Relevant for hinge, revolute joint, or assembly with connectors and mates. |
 | clearance-hole-through-plate | You need a through-hole sized for a bolt with a small clearance margin; cylinder height extends beyond the plate so the cut is unambiguous. |
 | extrude-rounded-rect-plate | You want a flat plate with rounded corners; use the dedicated rounded-rect extrude rather than building corners by hand. |
 | fillet-face-after-subtract | After subtracting a hole or pocket, you want to round only the rim of the resulting opening — not every edge in the part. |