# Skill Contract

**Skill ID:** add_cart_item
**Version:** v1
**Status:** APPROVED

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## Intent
To allow users to add a specific product by its item number and a desired quantity to their Century e-member shopping cart.

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## Inputs
- `item number` (string): The unique product code for the item to be added to the cart. This maps to `cart_procode`.
- `quantity` (integer): The number of units of the product to add to the cart. This maps to `cart_item_qty`.

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## Outputs
- `status` (boolean): Indicates if the operation was successful (`True`) or failed (`False`).
- `message` (string): A confirmation message on success or an error message on failure.
- `error_code` (integer, optional): An error code if the operation failed.

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## Output Message
successfully add item to cart

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## Logic
1.  Receive `item number` and `quantity` from the user.
2.  Validate that `item number` is a non-empty string and `quantity` is a positive integer.
3.  Call the `add_to_cart` MCP tool with the following parameters:
    -   `cart_procode`: Use the provided `item number`.
    -   `cart_item_qty`: Use the provided `quantity`.
4.  Upon receiving a response from the `add_to_cart` MCP tool:
    a.  Check the `error.status` field in the response.
    b.  If `error.status` is `False`, the item was successfully added to the cart. Return a success message (e.g., "successfully add item to cart").
    c.  If `error.status` is `True`, an error occurred. Extract the `error.msg` and `error.code` from the response and inform the user about the failure, including the specific error message and code.

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## Additional Logic
- Input Mode for collecting parameters from the user is `chat`.

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## Side Effects
- Modifies the user's shopping cart by adding a specified product and quantity in the Century e-member system via the `add_to_cart` MCP tool.

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## Capability Summary
This skill adds a specified product by its item number and quantity to the user's shopping cart using the `add_to_cart` MCP tool.

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## Allowed Roles
- SUPERUSER

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## Assumptions
- The `item number` provided by the user corresponds to a valid, existing product code in the Century e-member system.
- The `quantity` provided is a positive integer and available in stock.
- The `add_to_cart` MCP tool is operational and correctly handles requests and responses.
- The user's session or identity is correctly managed by the underlying MCP tool for cart modification.

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## Non-Goals
- Searching for product details or item numbers if they are unknown.
- Displaying the current contents of the shopping cart after adding an item.
- Updating the quantity of an item already in the cart (this is handled by `update_cart`).
- Removing items from the cart (this is handled by `remove_from_cart`).
- Handling complex business logic beyond direct addition, such as promotions or bundle deals.

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## Failure Modes
- **Invalid Input:** `item number` is empty or `quantity` is not a positive integer.
- **Product Not Found:** The provided `item number` does not correspond to an existing product.
- **Insufficient Stock:** The requested `quantity` exceeds available stock.
- **MCP Tool Error:** The `add_to_cart` MCP tool encounters an internal error or is unreachable.
- **Authentication Failure:** The user's session is invalid, preventing cart modification.
- **System Error:** The `add_to_cart` MCP tool returns `error.status: True` with a specific error message and code.

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## Data & System Access
- **External System:** Century e-member shopping cart system via the `add_to_cart` MCP tool.
- **Input Data:** `item number` (string), `quantity` (integer).
- **Output Data:** Response from `add_to_cart` tool containing `error.status`, `error.msg`, `error.code`.

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## Safety & Risk
Risk Level: MEDIUM

Risks include:
- **Incorrect Purchase:** Adding the wrong item or quantity to a user's cart, potentially leading to user frustration or incorrect orders.
- **System Overload:** High volume requests could strain the e-commerce system if not properly throttled by the MCP tool.
- **Data Integrity:** Errors in adding items could lead to inconsistencies in cart data.

Mitigation:
- Robust input validation to ensure `item number` and `quantity` are sensible.
- Clear error handling and informative messages to the user if an issue occurs during the `add_to_cart` operation.
- Relying on the `add_to_cart` MCP tool's inherent safety mechanisms and error reporting.

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## Input Mode
chat

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## Approval

    Approved by: USER  
    Approved on: 2026-05-07T00:56:52.575613Z