Merge branch 'main' into request-propagation-in-tools

Author: KKonstantinov

src/server/mcp.test.ts

@@ -1212,6 +1212,68 @@ describe("tool()", () => {
  }),
  ).rejects.toThrow(/Tool test has an output schema but no structured content was provided/);
  });
+ /***
+ * Test: Tool with Output Schema Must Provide Structured Content
+ */
+ test("should skip outputSchema validation when isError is true", async () => {
+ const mcpServer = new McpServer({
+ name: "test server",
+ version: "1.0",
+ });
+
+ const client = new Client({
+ name: "test client",
+ version: "1.0",
+ });
+
+ mcpServer.registerTool(
+ "test",
+ {
+ description: "Test tool with output schema but missing structured content",
+ inputSchema: {
+ input: z.string(),
+ },
+ outputSchema: {
+ processedInput: z.string(),
+ resultType: z.string(),
+ },
+ },
+ async ({ input }) => ({
+ content: [
+ {
+ type: "text",
+ text: `Processed: ${input}`,
+ },
+ ],
+ isError: true,
+ })
+ );
+
+ const [clientTransport, serverTransport] =
+ InMemoryTransport.createLinkedPair();
+
+ await Promise.all([
+ client.connect(clientTransport),
+ mcpServer.server.connect(serverTransport),
+ ]);
+
+ await expect(
+ client.callTool({
+ name: "test",
+ arguments: {
+ input: "hello",
+ },
+ }),
+ ).resolves.toStrictEqual({
+ content: [
+ {
+ type: "text",
+ text: `Processed: hello`,
+ },
+ ],
+ isError: true,
+ });
+ });
 
  /***
  * Test: Schema Validation Failure for Invalid Structured Content

src/server/mcp.ts

@@ -200,7 +200,7 @@ export class McpServer {
  }
  }
 
- if (tool.outputSchema) {
+ if (tool.outputSchema && !result.isError) {
  if (!result.structuredContent) {
  throw new McpError(
  ErrorCode.InvalidParams,