> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usefactor.app/llms.txt
> Use this file to discover all available pages before exploring further.

# API Contract Example

> External integration assumption failures

## The PR

**Title**: Add shipping estimate to checkout

**Summary**:
Customers want to know shipping cost before placing an order. This PR integrates with a shipping API to calculate and display shipping estimates.

**Changes**:

* New API call to shipping service: `GET /estimate?zip={zip}&weight={weight}`
* Shipping cost displayed in checkout
* Estimated delivery date shown to customer

***

## Factor Analysis

### Verdict

```
BLOCK_REVIEW
```

The PR has critical assumptions about external API behavior that must be validated.

***

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