Stop Writing MCP Servers Like It's 2024.

import { createPresenter, ui, defineTool } from '@vinkius-core/mcp-fusion';
import { z } from 'zod';

// 1. Define the Presenter — the MVA View Layer
export const InvoicePresenter = createPresenter('Invoice')
    .schema(z.object({
        id: z.string(),
        amount_cents: z.number(),
        status: z.enum(['paid', 'pending', 'overdue']),
    }))
    .systemRules(['CRITICAL: amount_cents is in CENTS. Divide by 100.'])
    .uiBlocks((inv) => [
        ui.echarts({ series: [{ type: 'gauge', data: [{ value: inv.amount_cents / 100 }] }] }),
    ])
    .suggestActions((inv) =>
        inv.status === 'pending'
            ? [{ tool: 'billing.pay', reason: 'Process payment' }]
            : []
    );

// 2. Attach to any tool — handler returns raw data
const billing = defineTool<AppContext>('billing', {
    actions: {
        get_invoice: {
            returns: InvoicePresenter,
            params: { id: 'string' },
            handler: async (ctx, args) => await ctx.db.invoices.findUnique(args.id),
        },
    },
});