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test(server): cover non-object output schemas #2533

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ad1a897
test(server): cover zod output schema wrappers
pradeep-ramola Jul 21, 2026
4f0debd
test(server): cover non-object output schemas
pradeep-ramola Jul 22, 2026
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58 changes: 55 additions & 3 deletions test/integration/test/server/createMcpHandler.test.ts
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ import { afterEach, describe, expect, it } from 'vitest';
import * as z from 'zod/v4';

const MODERN = '2026-07-28';
type ServerFactory = (ctx: McpRequestContext) => McpServer;

describe('createMcpHandler over HTTP (legacy postures end to end)', () => {
const cleanups: Array<() => Promise<void> | void> = [];
Expand All @@ -31,7 +32,7 @@ describe('createMcpHandler over HTTP (legacy postures end to end)', () => {

// One factory for both legs: the era only shows up in the tool output so the
// tests can see which leg served the call.
const factory = (ctx: McpRequestContext) => {
const factory: ServerFactory = (ctx: McpRequestContext) => {
const mcpServer = new McpServer(
{ name: 'dual-era-endpoint', version: '1.0.0' },
{ capabilities: { tools: {} }, instructions: 'dual era endpoint' }
Expand All @@ -42,8 +43,11 @@ describe('createMcpHandler over HTTP (legacy postures end to end)', () => {
return mcpServer;
};

async function startEndpoint(options?: CreateMcpHandlerOptions): Promise<{ baseUrl: URL; handler: McpHttpHandler }> {
const handler = createMcpHandler(factory, options);
async function startEndpoint(
options?: CreateMcpHandlerOptions,
serverFactory: ServerFactory = factory
): Promise<{ baseUrl: URL; handler: McpHttpHandler }> {
const handler = createMcpHandler(serverFactory, options);
const httpServer: HttpServer = createServer(toNodeHandler(handler));
const baseUrl = await listenOnRandomPort(httpServer);
cleanups.push(async () => {
Expand Down Expand Up @@ -114,6 +118,54 @@ describe('createMcpHandler over HTTP (legacy postures end to end)', () => {
expect(bodies[0]).toContain('server/discover');
});

it('preserves non-object tool output schemas and structured content for modern clients', async () => {
const { baseUrl } = await startEndpoint(undefined, () => {
const mcpServer = new McpServer({ name: 'non-object-output', version: '1.0.0' }, { capabilities: { tools: {} } });
mcpServer.registerTool(
'string-output',
{
outputSchema: z.string()
},
() => ({
structuredContent: 'pong'
})
);
mcpServer.registerTool(
'array-output',
{
outputSchema: z.array(z.string())
},
() => ({
structuredContent: ['alpha', 'beta']
})
);
return mcpServer;
});

const client = new Client({ name: 'modern-client', version: '1.0.0' }, { versionNegotiation: { mode: 'auto' } });
await client.connect(new StreamableHTTPClientTransport(baseUrl));
cleanups.push(() => client.close());

expect(client.getNegotiatedProtocolVersion()).toBe(MODERN);

const { tools } = await client.listTools();
expect(tools.find(tool => tool.name === 'string-output')?.outputSchema).toMatchObject({
type: 'string'
});
expect(tools.find(tool => tool.name === 'array-output')?.outputSchema).toMatchObject({
type: 'array',
items: { type: 'string' }
});

const stringResult = await client.callTool({ name: 'string-output', arguments: {} });
expect(stringResult.structuredContent).toBe('pong');
expect(stringResult.content).toContainEqual({ type: 'text', text: '"pong"' });

const arrayResult = await client.callTool({ name: 'array-output', arguments: {} });
expect(arrayResult.structuredContent).toEqual(['alpha', 'beta']);
expect(arrayResult.content).toContainEqual({ type: 'text', text: '["alpha","beta"]' });
});

it('answers an envelope claiming an unsupported revision with the supported list over plain HTTP', async () => {
const { baseUrl } = await startEndpoint();

Expand Down
171 changes: 171 additions & 0 deletions test/integration/test/server/mcp.test.ts
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1359,6 +1359,177 @@ describe('Zod v4', () => {
expect(JSON.parse(textContent.text)).toEqual(result.structuredContent);
});

test('should validate outputSchema when using Zod schema wrappers and non-object roots', async () => {
const mcpServer = new McpServer({
name: 'test server',
version: '1.0'
});

const client = new Client({
name: 'test client',
version: '1.0'
});

mcpServer.registerTool(
'optional-output',
{
outputSchema: z.object({ data: z.string() }).optional()
},
async () => ({
structuredContent: { data: 'optional' }
})
);

const unionOutputSchema = z.union([z.object({ data: z.string() }), z.object({ value: z.string() })]);

mcpServer.registerTool(
'union-output',
{
outputSchema: unionOutputSchema
},
async () => ({
structuredContent: { value: 'union' }
})
);

mcpServer.registerTool(
'invalid-union-output',
{
outputSchema: unionOutputSchema
},
async () => ({
structuredContent: { invalid: true }
})
);

mcpServer.registerTool(
'string-output',
{
outputSchema: z.string()
},
async () => ({
structuredContent: 'pong'
})
);

mcpServer.registerTool(
'array-output',
{
outputSchema: z.array(z.string())
},
async () => ({
structuredContent: ['alpha', 'beta']
})
);

mcpServer.registerTool(
'invalid-string-output',
{
outputSchema: z.string()
},
async () => ({
structuredContent: 123
})
);

mcpServer.registerTool(
'invalid-array-output',
{
outputSchema: z.array(z.string())
},
async () => ({
structuredContent: ['ok', 1]
})
);

const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();

await Promise.all([client.connect(clientTransport), mcpServer.server.connect(serverTransport)]);

const listResult = await client.request({ method: 'tools/list' });
expect(listResult.tools.find(tool => tool.name === 'string-output')?.outputSchema).toMatchObject({
type: 'object',
properties: { result: { type: 'string' } },
required: ['result']
});
expect(listResult.tools.find(tool => tool.name === 'array-output')?.outputSchema).toMatchObject({
type: 'object',
properties: { result: { type: 'array', items: { type: 'string' } } },
required: ['result']
});

const optionalResult = await client.callTool({
name: 'optional-output'
});
expect(optionalResult.structuredContent).toEqual({ data: 'optional' });

const unionResult = await client.callTool({
name: 'union-output'
});
expect(unionResult.structuredContent).toEqual({ value: 'union' });

const stringResult = await client.callTool({
name: 'string-output'
});
expect(stringResult.structuredContent).toEqual({ result: 'pong' });
expect(stringResult.content).toEqual([
{
type: 'text',
text: '"pong"'
}
]);

const arrayResult = await client.callTool({
name: 'array-output'
});
expect(arrayResult.structuredContent).toEqual({ result: ['alpha', 'beta'] });
expect(arrayResult.content).toEqual([
{
type: 'text',
text: '["alpha","beta"]'
}
]);

const invalidUnionResult = await client.callTool({
name: 'invalid-union-output'
});
expect(invalidUnionResult.isError).toBe(true);
expect(invalidUnionResult.content).toEqual(
expect.arrayContaining([
{
type: 'text',
text: expect.stringContaining('Output validation error: Invalid structured content for tool invalid-union-output')
}
])
);

const invalidStringResult = await client.callTool({
name: 'invalid-string-output'
});
expect(invalidStringResult.isError).toBe(true);
expect(invalidStringResult.content).toEqual(
expect.arrayContaining([
{
type: 'text',
text: expect.stringContaining('Output validation error: Invalid structured content for tool invalid-string-output')
}
])
);

const invalidArrayResult = await client.callTool({
name: 'invalid-array-output'
});
expect(invalidArrayResult.isError).toBe(true);
expect(invalidArrayResult.content).toEqual(
expect.arrayContaining([
{
type: 'text',
text: expect.stringContaining('Output validation error: Invalid structured content for tool invalid-array-output')
}
])
);
});

/***
* Test: Tool with Output Schema Must Provide Structured Content
*/
Expand Down
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