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

# Compare Products

> Side-by-side comparison of two or more products on price, certifications, ingredients, and provenance.

Given 2+ GTINs, produce a structured diff covering what matters for a
purchase decision: price, certifications, ingredients/substances, net
content, country of origin, brand ownership.

## When to use

* User says "which of these is better?" or "what's the difference?"
* Following `find-alternative` to justify why the alternative wins.
* Before `plan-shopping-trip` to pick between two viable candidates.

## Flow

Closient does not yet have a single comparison endpoint. The pattern is:

### 1. Fetch each product

```
GET /products/api/v1/products/{gtin_a}
GET /products/api/v1/products/{gtin_b}
```

### 2. Fetch side data per GTIN

* `GET /certifications/api/v1/products/{gtin}` — certifications held
* `GET /compliance/api/v1/products/{gtin}/recalls?status=ONGOING` — any
  active recalls (dealbreaker!)
* If location is known, optionally `check-product-availability` for stock
  * price per store

### 3. Structure the diff

Group by category so the user can scan:

```
Price:            A=$4.99   B=$5.49
Net content:      A=946 mL  B=1 L
Certifications:   A=[organic, non-gmo]   B=[organic]
Country:          A=USA     B=Canada
Data confidence:  A=0.93    B=0.88
Active recalls:   A=none    B=none
```

### 4. Highlight meaningful differences

* Certifications one has that the other lacks
* Price per unit (normalize by net\_content)
* Brand ownership / claim status
* Any recall on either → surface as critical

## Guidance for agents

* **Normalize units**: report price per standard unit (per 100 mL, per 100 g)
  rather than raw price; lets the user compare apples to apples.
* **Cite data quality**: if `confidence_score < 0.7` on a critical field,
  note that the data is inferred.
* **Recalls are a hard flag**: any CLASS\_I recall means that option is out.

## Planned

A single `POST /products/api/v1/compare` endpoint accepting N GTINs and
returning a structured diff with pre-normalized fields.

## Related skills

* `resolve-gtin` — for each product being compared
* `check-recalls` — critical safety check per candidate
* `find-alternative` — often ends by calling this to justify the pick