feat(config-audit): MCP tool-count detection with manifest fallback (v5 M1) [skip-docs]

readActiveMcpServers now resolves tool count via:
  1. In-config tools array
  2. Cached tools/list at \$HOME/.claude/config-audit/mcp-cache/<name>.json
  3. node_modules/<pkg>/package.json (resolved from npx <pkg>)
  4. Fallback: { toolCount: null, toolCountUnknown: true }

estimateTokens uses detected toolCount (heavy server > light server).

New fixture: mcp-tool-heavy/ with mocked node_modules/mcp-heavy/package.json (20 tools).

576 → 580 tests, all green.

plugins/config-audit/tests/fixtures/mcp-tool-heavy/.mcp.json

@@ -0,0 +1,6 @@
+{
+  "mcpServers": {
+    "heavy": { "command": "npx", "args": ["mcp-heavy"] },
+    "light": { "command": "npx", "args": ["mcp-light"] }
+  }
+}

plugins/config-audit/tests/lib/active-config-reader.test.mjs

@@ -539,6 +539,70 @@ describe('readActiveMcpServers', () => {
   });
 });
 
+// ─────────────────────────────────────────────────────────────────────────
+// readActiveMcpServers — tool-count detection (v5 M1)
+// ─────────────────────────────────────────────────────────────────────────
+
+describe('readActiveMcpServers — tool-count detection (v5 M1)', () => {
+  it('detects toolCount from project node_modules/<pkg>/package.json', async () => {
+    const fixturePath = resolve(import.meta.dirname || dirname(new URL(import.meta.url).pathname),
+      '..', 'fixtures', 'mcp-tool-heavy');
+    const servers = await readActiveMcpServers(fixturePath);
+    const heavy = servers.find(s => s.name === 'heavy');
+    assert.ok(heavy, 'expected heavy server from fixture');
+    assert.equal(heavy.toolCount, 20, `expected toolCount=20, got ${heavy.toolCount}`);
+    assert.equal(heavy.toolCountUnknown, false);
+  });
+
+  it('falls back to toolCount: null + toolCountUnknown: true when manifest missing', async () => {
+    const fixturePath = resolve(import.meta.dirname || dirname(new URL(import.meta.url).pathname),
+      '..', 'fixtures', 'mcp-tool-heavy');
+    const servers = await readActiveMcpServers(fixturePath);
+    const light = servers.find(s => s.name === 'light');
+    assert.ok(light, 'expected light server from fixture');
+    assert.equal(light.toolCount, null);
+    assert.equal(light.toolCountUnknown, true);
+  });
+
+  it('detects toolCount from cache file in $HOME/.claude/config-audit/mcp-cache/', async () => {
+    const fakeHome = uniqueDir('mcp-cache');
+    const repoRoot = uniqueDir('mcp-cache-repo');
+    await mkdir(repoRoot, { recursive: true });
+    await writeFile(
+      join(repoRoot, '.mcp.json'),
+      JSON.stringify({ mcpServers: { cached: { command: 'npx', args: ['unknown-pkg'] } } }, null, 2),
+    );
+    await mkdir(join(fakeHome, '.claude', 'config-audit', 'mcp-cache'), { recursive: true });
+    await writeFile(
+      join(fakeHome, '.claude', 'config-audit', 'mcp-cache', 'cached.json'),
+      JSON.stringify({ tools: Array.from({ length: 12 }, (_, i) => ({ name: `t${i}` })) }, null, 2),
+    );
+    const originalHome = process.env.HOME;
+    process.env.HOME = fakeHome;
+    try {
+      const servers = await readActiveMcpServers(repoRoot);
+      const cached = servers.find(s => s.name === 'cached');
+      assert.ok(cached, 'expected cached server');
+      assert.equal(cached.toolCount, 12, `expected toolCount=12 from cache, got ${cached.toolCount}`);
+      assert.equal(cached.toolCountUnknown, false);
+    } finally {
+      process.env.HOME = originalHome;
+      await rm(fakeHome, { recursive: true, force: true });
+      await rm(repoRoot, { recursive: true, force: true });
+    }
+  });
+
+  it('toolCount drives estimateTokens (heavy > light)', async () => {
+    const fixturePath = resolve(import.meta.dirname || dirname(new URL(import.meta.url).pathname),
+      '..', 'fixtures', 'mcp-tool-heavy');
+    const servers = await readActiveMcpServers(fixturePath);
+    const heavy = servers.find(s => s.name === 'heavy');
+    const light = servers.find(s => s.name === 'light');
+    assert.ok(heavy.estimatedTokens > light.estimatedTokens,
+      `expected heavy (${heavy.estimatedTokens}) > light (${light.estimatedTokens})`);
+  });
+});
+
 // ─────────────────────────────────────────────────────────────────────────
 // readActiveConfig (integration)
 // ─────────────────────────────────────────────────────────────────────────