feat(core): Implement Test workflow MCP tool (n8n-io#27348)

Author: MiloradFilipovic

packages/@n8n/workflow-sdk/src/generate-types/index.ts

@@ -78,5 +78,8 @@ export {
 	planSplitVersionSchemaFiles,
 } from './generate-zod-schemas';
 
+// JSON Schema inference from data
+export { generateJsonSchemaFromData } from './json-schema-from-data';
+
 // Zod helpers (for use in generated files)
 export * from './zod-helpers';

packages/@n8n/workflow-sdk/src/generate-types/json-schema-from-data.test.ts

@@ -0,0 +1,81 @@
+import { generateJsonSchemaFromData } from './json-schema-from-data';
+
+describe('generateJsonSchemaFromData', () => {
+	it('infers string type', () => {
+		expect(generateJsonSchemaFromData('hello')).toEqual({ type: 'string' });
+	});
+
+	it('infers number type', () => {
+		expect(generateJsonSchemaFromData(42)).toEqual({ type: 'number' });
+	});
+
+	it('infers boolean type', () => {
+		expect(generateJsonSchemaFromData(true)).toEqual({ type: 'boolean' });
+	});
+
+	it('infers null type', () => {
+		expect(generateJsonSchemaFromData(null)).toEqual({ type: 'null' });
+	});
+
+	it('infers undefined as null', () => {
+		expect(generateJsonSchemaFromData(undefined)).toEqual({ type: 'null' });
+	});
+
+	it('infers flat object', () => {
+		expect(generateJsonSchemaFromData({ name: 'test', count: 5 })).toEqual({
+			type: 'object',
+			properties: {
+				name: { type: 'string' },
+				count: { type: 'number' },
+			},
+			required: ['name', 'count'],
+		});
+	});
+
+	it('infers nested object', () => {
+		expect(generateJsonSchemaFromData({ user: { email: 'a@b.com', active: true } })).toEqual({
+			type: 'object',
+			properties: {
+				user: {
+					type: 'object',
+					properties: {
+						email: { type: 'string' },
+						active: { type: 'boolean' },
+					},
+					required: ['email', 'active'],
+				},
+			},
+			required: ['user'],
+		});
+	});
+
+	it('infers array with items', () => {
+		expect(generateJsonSchemaFromData([{ id: 1 }])).toEqual({
+			type: 'array',
+			items: {
+				type: 'object',
+				properties: {
+					id: { type: 'number' },
+				},
+				required: ['id'],
+			},
+		});
+	});
+
+	it('infers empty array', () => {
+		expect(generateJsonSchemaFromData([])).toEqual({
+			type: 'array',
+			items: {},
+		});
+	});
+
+	it('does not retain actual values', () => {
+		const data = { secret: 'my-api-key', email: 'user@private.com', count: 999 };
+		const schema = generateJsonSchemaFromData(data);
+
+		const json = JSON.stringify(schema);
+		expect(json).not.toContain('my-api-key');
+		expect(json).not.toContain('user@private.com');
+		expect(json).not.toContain('999');
+	});
+});

packages/@n8n/workflow-sdk/src/generate-types/json-schema-from-data.ts

@@ -0,0 +1,50 @@
+/**
+ * JSON Schema from Data Inferrer
+ *
+ * Infers a JSON Schema from a concrete data value.
+ * Used to derive output shapes from execution history without
+ * exposing the actual data values.
+ */
+
+import type { JsonSchema } from './generate-types';
+
+/**
+ * Infer a JSON Schema from a concrete data value.
+ *
+ * Recursively inspects the value to produce a schema describing
+ * its shape (types, property names, array item types) without
+ * retaining any of the original values.
+ */
+export function generateJsonSchemaFromData(value: unknown): JsonSchema {
+	if (value === null || value === undefined) {
+		return { type: 'null' };
+	}
+
+	const type = typeof value;
+
+	if (type === 'string') return { type: 'string' };
+	if (type === 'number') return { type: 'number' };
+	if (type === 'boolean') return { type: 'boolean' };
+
+	if (Array.isArray(value)) {
+		return {
+			type: 'array',
+			items: value.length > 0 ? generateJsonSchemaFromData(value[0]) : {},
+		};
+	}
+
+	if (type === 'object') {
+		const properties: Record<string, JsonSchema> = {};
+		for (const [key, propValue] of Object.entries(value as Record<string, unknown>)) {
+			properties[key] = generateJsonSchemaFromData(propValue);
+		}
+		const keys = Object.keys(properties);
+		return {
+			type: 'object',
+			properties,
+			...(keys.length > 0 && { required: keys }),
+		};
+	}
+
+	return { type: 'string' };
+}

packages/@n8n/workflow-sdk/src/index.ts

@@ -179,6 +179,15 @@ export {
 	type SerializerPlugin,
 } from './workflow-builder/plugins';
 
+// Pin data utilities
+export {
+	needsPinData,
+	discoverOutputSchemaForNode,
+	inferSchemasFromRunData,
+	normalizePinData,
+	type IsTriggerNodeFn,
+} from './pin-data-utils';
+
 // Node type constants
 export {
 	NODE_TYPES,