test(e2e): add MCP error tool e2e test for span.status=internal_error

Adds an `always-error` tool to the MCP e2e test apps and a test step
that verifies the resulting transaction has span.status=internal_error
when a tool throws. This covers the fix in the span status correlation
path end-to-end, complementing the existing unit tests.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Author: betegon

dev-packages/e2e-tests/test-applications/node-express-v5/src/mcp.ts

@@ -47,6 +47,10 @@ server.prompt('echo', { message: z.string() }, ({ message }, extra) => ({
   ],
 }));
 
+server.tool('always-error', {}, async () => {
+  throw new Error('intentional error for span status testing');
+});
+
 const transports: Record<string, SSEServerTransport> = {};
 
 mcpRouter.get('/sse', async (_, res) => {

dev-packages/e2e-tests/test-applications/node-express-v5/tests/mcp.test.ts

@@ -120,6 +120,23 @@ test('Should record transactions for mcp handlers', async ({ baseURL }) => {
 
     // TODO: When https://github.com/modelcontextprotocol/typescript-sdk/pull/358 is released check for trace id equality between the post transaction and the handler transaction
   });
+
+  await test.step('error tool sets span status to internal_error', async () => {
+    const toolTransactionPromise = waitForTransaction('node-express-v5', transactionEvent => {
+      return transactionEvent.transaction === 'tools/call always-error';
+    });
+
+    try {
+      await client.callTool({ name: 'always-error', arguments: {} });
+    } catch {
+      // Expected: MCP SDK throws when the tool returns a JSON-RPC error
+    }
+
+    const toolTransaction = await toolTransactionPromise;
+    expect(toolTransaction).toBeDefined();
+    expect(toolTransaction.contexts?.trace?.op).toEqual('mcp.server');
+    expect(toolTransaction.contexts?.trace?.status).toEqual('internal_error');
+  });
 });
 
 /**

dev-packages/e2e-tests/test-applications/node-express/src/mcp.ts

@@ -47,6 +47,10 @@ server.prompt('echo', { message: z.string() }, ({ message }, extra) => ({
   ],
 }));
 
+server.tool('always-error', {}, async () => {
+  throw new Error('intentional error for span status testing');
+});
+
 const transports: Record<string, SSEServerTransport> = {};
 
 mcpRouter.get('/sse', async (_, res) => {

dev-packages/e2e-tests/test-applications/node-express/tests/mcp.test.ts

@@ -126,6 +126,23 @@ test('Should record transactions for mcp handlers', async ({ baseURL }) => {
     expect(promptTransaction.contexts?.trace?.data?.['mcp.method.name']).toEqual('prompts/get');
     // TODO: When https://github.com/modelcontextprotocol/typescript-sdk/pull/358 is released check for trace id equality between the post transaction and the handler transaction
   });
+
+  await test.step('error tool sets span status to internal_error', async () => {
+    const toolTransactionPromise = waitForTransaction('node-express', transactionEvent => {
+      return transactionEvent.transaction === 'tools/call always-error';
+    });
+
+    try {
+      await client.callTool({ name: 'always-error', arguments: {} });
+    } catch {
+      // Expected: MCP SDK throws when the tool returns a JSON-RPC error
+    }
+
+    const toolTransaction = await toolTransactionPromise;
+    expect(toolTransaction).toBeDefined();
+    expect(toolTransaction.contexts?.trace?.op).toEqual('mcp.server');
+    expect(toolTransaction.contexts?.trace?.status).toEqual('internal_error');
+  });
 });
 
 /**

dev-packages/e2e-tests/test-applications/tsx-express/src/mcp.ts

@@ -47,6 +47,10 @@ server.prompt('echo', { message: z.string() }, ({ message }, extra) => ({
   ],
 }));
 
+server.tool('always-error', {}, async () => {
+  throw new Error('intentional error for span status testing');
+});
+
 const transports: Record<string, SSEServerTransport> = {};
 
 mcpRouter.get('/sse', async (_, res) => {

dev-packages/e2e-tests/test-applications/tsx-express/tests/mcp.test.ts

@@ -123,6 +123,23 @@ test('Records transactions for mcp handlers', async ({ baseURL }) => {
 
     // TODO: When https://github.com/modelcontextprotocol/typescript-sdk/pull/358 is released check for trace id equality between the post transaction and the handler transaction
   });
+
+  await test.step('error tool sets span status to internal_error', async () => {
+    const toolTransactionPromise = waitForTransaction('tsx-express', transactionEvent => {
+      return transactionEvent.transaction === 'tools/call always-error';
+    });
+
+    try {
+      await client.callTool({ name: 'always-error', arguments: {} });
+    } catch {
+      // Expected: MCP SDK throws when the tool returns a JSON-RPC error
+    }
+
+    const toolTransaction = await toolTransactionPromise;
+    expect(toolTransaction).toBeDefined();
+    expect(toolTransaction.contexts?.trace?.op).toEqual('mcp.server');
+    expect(toolTransaction.contexts?.trace?.status).toEqual('internal_error');
+  });
 });
 
 /**