feat(api-contract): add SDK and MCP-specific contract exports

Add sdkContract and mcpContract exports that contain only the methods
each router implements. This allows proper TypeScript validation while
keeping the unified contract for type sharing.

- sdkContract: checkout.get/create/confirm/etc, onboarding.*, products.list
- mcpContract: customer.*, order.*, checkout.list/get (summary), products.*
- Add CheckoutListItemSchema and CheckoutDetailSchema for MCP endpoints
- These are simpler than the full CheckoutSchema used by SDK

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: npslaney

src/contracts/checkout.ts

@@ -167,11 +167,65 @@ export const listCheckoutsContract = oc
 	.input(ListCheckoutsInputSchema)
 	.output(ListCheckoutsOutputSchema);
 
+// MCP-specific embedded customer schema
+const CheckoutCustomerSchema = z
+	.object({
+		id: z.string(),
+		name: z.string().nullable(),
+		email: z.string().nullable(),
+		emailVerified: z.boolean(),
+		externalId: z.string().nullable(),
+		userMetadata: z.record(z.unknown()).nullable(),
+		organizationId: z.string(),
+		createdAt: z.date(),
+		modifiedAt: z.date().nullable(),
+	})
+	.nullable();
+
+// MCP-specific summary schema for list (simpler than full CheckoutSchema)
+const CheckoutListItemSchema = z.object({
+	id: z.string(),
+	status: CheckoutStatusSchema,
+	type: z.enum(["PRODUCTS", "AMOUNT", "TOP_UP"]),
+	currency: CurrencySchema,
+	totalAmount: z.number().nullable(),
+	customerId: z.string().nullable(),
+	customer: CheckoutCustomerSchema,
+	productId: z.string().nullable(),
+	organizationId: z.string(),
+	expiresAt: z.date(),
+	createdAt: z.date(),
+	modifiedAt: z.date().nullable(),
+});
+
+// MCP-specific detailed schema for get (includes additional fields)
+const CheckoutDetailSchema = CheckoutListItemSchema.extend({
+	userMetadata: z.record(z.unknown()).nullable(),
+	successUrl: z.string().nullable(),
+	discountAmount: z.number().nullable(),
+	netAmount: z.number().nullable(),
+	taxAmount: z.number().nullable(),
+});
+
+const ListCheckoutsSummaryOutputSchema = PaginationOutputSchema.extend({
+	checkouts: z.array(CheckoutListItemSchema),
+});
+
+export const listCheckoutsSummaryContract = oc
+	.input(ListCheckoutsInputSchema)
+	.output(ListCheckoutsSummaryOutputSchema);
+
+export const getCheckoutSummaryContract = oc
+	.input(GetCheckoutInputSchema)
+	.output(CheckoutDetailSchema);
+
 export const checkout = {
 	get: getCheckoutContract,
 	create: createCheckoutContract,
 	confirm: confirmCheckoutContract,
 	registerInvoice: registerInvoiceContract,
 	paymentReceived: paymentReceivedContract,
 	list: listCheckoutsContract,
+	listSummary: listCheckoutsSummaryContract,
+	getSummary: getCheckoutSummaryContract,
 };

src/index.ts

@@ -53,9 +53,35 @@ export {
 	RecurringIntervalInputSchema,
 } from "./schemas/product-price-input";
 
-// Unified contract - consumed by both SDK and MCP
+// Unified contract - contains all methods from both SDK and MCP
 export const contract = { checkout, customer, onboarding, order, products };
 
+// SDK contract - only the methods the SDK router implements
+export const sdkContract = {
+	checkout: {
+		get: checkout.get,
+		create: checkout.create,
+		confirm: checkout.confirm,
+		registerInvoice: checkout.registerInvoice,
+		paymentReceived: checkout.paymentReceived,
+	},
+	onboarding,
+	products: {
+		list: products.list,
+	},
+};
+
+// MCP contract - only the methods the MCP router implements
+export const mcpContract = {
+	customer,
+	order,
+	checkout: {
+		list: checkout.listSummary,
+		get: checkout.getSummary,
+	},
+	products,
+};
+
 export type { MetadataValidationError } from "./validation/metadata-validation";
 export {
 	MAX_KEY_COUNT,