feat: Disable MCP if ai_monitoring disabled (#3276)

Author: amychisholm03

lib/subscribers/mcp-sdk/client.js

@@ -12,7 +12,12 @@ class McpClientSubscriber extends Subscriber {
     super({ agent, logger, packageName: '@modelcontextprotocol/sdk', channelName })
     this.events = ['asyncEnd']
     this.requireActiveTx = true
-    this.segmentName = ''
+    this.segmentName = 'Unknown'
+  }
+
+  get enabled() {
+    return this.config.instrumentation[this.packageName].enabled === true &&
+    this.config.ai_monitoring.enabled === true
   }
 
   handler(ctx) {

test/unit/shimmer.test.js

@@ -824,7 +824,8 @@ test('Shimmer with logger mock', async (t) => {
 
     require(TEST_MODULE_RELATIVE_PATH)
     const version = shimmer.getPackageVersion(TEST_MODULE_PATH)
-    assert.ok(!loggerMock.debug.callCount)
+    const found = loggerMock.debug.args.find(debugArgs => debugArgs?.[0]?.includes('Failed to get version for `%s`, reason: %s'))
+    assert.equal(undefined, found)
     assert.equal(version, '0.0.1', 'should get package version from package.json')
   })
 
@@ -833,7 +834,7 @@ test('Shimmer with logger mock', async (t) => {
     () => {
       const version = shimmer.getPackageVersion('bogus')
       assert.equal(version, process.version)
-      assert.deepEqual(loggerMock.debug.args[0], [
+      assert.deepEqual(loggerMock.debug.args[loggerMock.debug.args.length - 1], [
         'Failed to get version for `%s`, reason: %s',
         'bogus',
         "no tracked items for module 'bogus'"

test/versioned/mcp-sdk/client.test.js

@@ -18,7 +18,11 @@ const {
 
 test.beforeEach(async (ctx) => {
   ctx.nr = {}
-  ctx.nr.agent = helper.instrumentMockedAgent({})
+  ctx.nr.agent = helper.instrumentMockedAgent({
+    ai_monitoring: {
+      enabled: ctx.name.includes('disabled') ? false : true
+    }
+  })
 
   const { Client } = require('@modelcontextprotocol/sdk/client/index.js')
   const { StdioClientTransport } = require('@modelcontextprotocol/sdk/client/stdio.js')
@@ -54,6 +58,7 @@ test('should create span for callTool', async (t) => {
     assert.ok(result, 'should return a result from the tool call')
 
     const name = `${MCP.TOOL}/callTool/echo`
+    assert.equal(tx.trace.transaction.numSegments, 3, 'should have 3 segments')
     assertSegments(tx.trace, tx.trace.root, [name], { exact: false })
 
     tx.end()
@@ -112,3 +117,22 @@ test('should create span for getPrompt', async (t) => {
     })
   })
 })
+
+test('should not instrument if ai_monitoring is disabled', async (t) => {
+  const { agent, client } = t.nr
+
+  await helper.runInTransaction(agent, async (tx) => {
+    const result = await client.callTool({
+      name: 'echo',
+      arguments: {
+        message: 'example message'
+      }
+    })
+
+    assert.ok(result, 'should still return a result from the tool call')
+
+    assert.equal(tx.trace.transaction.numSegments, 2, 'should not create MCP segment')
+
+    tx.end()
+  })
+})