fakestore_update_cart

Modify cart details like user ID, date, or products in a simulated e-commerce environment for testing and development purposes.

Instructions

Update an existing cart (simulation - does not persist)

Input Schema

TableJSON Schema

Name	Required	Description
`id`	Yes	Cart ID to update
`userId`	No	New user ID
`date`	No	New cart date
`products`	No	New products array

Implementation Reference

src/tools/carts.ts:81-105 (handler)

Core handler function that validates the input arguments and performs the PUT request to update the cart on the FakeStore API.

export async function updateCart(args: {
  id: number;
  userId?: number;
  date?: string;
  products?: CartProduct[];
}): Promise<Cart> {
  const { id, userId, date, products } = args;
  validatePositiveInteger(id, 'Cart ID');

  const updateData: Record<string, unknown> = {};
  if (userId !== undefined) {
    validatePositiveInteger(userId, 'User ID');
    updateData.userId = userId;
  }
  if (date !== undefined) {
    validateISODate(date, 'Date');
    updateData.date = date;
  }
  if (products !== undefined) {
    validateNonEmptyArray<CartProduct>(products, 'Products');
    updateData.products = products;
  }

  return put<Cart>(`/carts/${id}`, updateData);
}

src/index.ts:149-159 (handler)

Top-level dispatch handler in the MCP server that matches the tool name and invokes the updateCart function with typed arguments, returning the JSON stringified result.

if (name === 'fakestore_update_cart') {
  const result = await updateCart(args as {
    id: number;
    userId?: number;
    date?: string;
    products?: Array<{ productId: number; quantity: number }>;
  });
  return {
    content: [{ type: 'text', text: JSON.stringify(result, null, 2) }],
  };
}

src/tools/carts.ts:202-241 (schema)

Tool schema definition including name, description, and inputSchema for validation in the MCP tool list.

{
  name: 'fakestore_update_cart',
  description: 'Update an existing cart (simulation - does not persist)',
  inputSchema: {
    type: 'object',
    properties: {
      id: {
        type: 'number',
        description: 'Cart ID to update',
      },
      userId: {
        type: 'number',
        description: 'New user ID',
      },
      date: {
        type: 'string',
        description: 'New cart date',
      },
      products: {
        type: 'array',
        description: 'New products array',
        items: {
          type: 'object',
          properties: {
            productId: {
              type: 'number',
              description: 'Product ID',
            },
            quantity: {
              type: 'number',
              description: 'Product quantity',
            },
          },
          required: ['productId', 'quantity'],
        },
      },
    },
    required: ['id'],
  },
},

src/index.ts:40-44 (registration)
Registration of all tools including cartTools (which contains fakestore_update_cart) in the MCP listTools handler.
```
server.setRequestHandler(ListToolsRequestSchema, async () => {
  return {
    tools: [...productTools, ...cartTools, ...userTools],
  };
});
```

Fake Store API MCP Server