Updated October 31, 2026 · from public documentation
Ways for AI agents to buy, compared.
If you are building an agent that buys things, these are the main options in late 2026. Each solves a different part of the problem. We build Kaupia, so read this with that in mind; corrections are welcome at [email protected].
| Option | Built for | Where products come from | How checkout works | Published pricing |
|---|---|---|---|---|
| Kaupia | Any AI agent (MCP) and the stores that sell to them | Store catalogs via UCP, starting with Shopify’s Global Catalog; store onboarding in early access | Store’s own checkout for the exact variant and quantity; outcomes reported back and used for ranking | Free for agents in early access; stores pay a commission only on completed agent orders |
| Shopify Global Catalog | Agent developers | Shopify merchants, plus brands on Shopify’s Agentic plan | Checkout links into Shopify checkout | No API key needed for the catalog; search results may not be cached |
| Rye — Universal Checkout API | Agent developers | Any merchant by product URL; direct integrations for Amazon and Shopify, browser automation as fallback | Rye places the order through its API | $149/month (first month free); separate Sync API priced on GMV |
| Crossmint — Agent Checkouts | Agent developers | Amazon, Shopify and more, by product URL or ID | Crossmint completes checkout as merchant of record, within a spending cap; production access is enterprise | Not published |
| Zinc | Developers | Large retailers such as Amazon, Walmart and Target, through managed accounts | Zinc places orders from a prefunded wallet | About $1 per successful order plus $0.01 per data call |
| firmly | Merchants and the AI or social channels that sell for them | Merchants that connect through firmly | Merchant stays merchant of record; checkout embedded in partner channels such as Perplexity | Not published |
| Amazon Buy for Me | Shoppers in the Amazon app | Outside brands’ websites listed through Amazon | Amazon’s agent buys on the brand’s own site | Reported as no commission during the test |
How to choose
- You want one tool that any agent can call, across many stores, with outcome‑based ranking: Kaupia.
- You only need Shopify inventory: Shopify’s Global Catalog directly.
- You need to buy from a specific URL at any merchant, and will pay a monthly fee: Rye.
- You want a merchant of record that handles the whole transaction: Crossmint.
- You buy mostly from Amazon, Walmart or Target: Zinc.
- You are a merchant who wants to appear inside AI and social channels: firmly — or list on Kaupia to reach any MCP agent.
Sources
- Shopify Dev — Catalogs: https://shopify.dev/docs/agents/catalog
- Shopify — Agentic plan: https://www.shopify.com/news/agentic-commerce-momentum
- Rye — API comparison and pricing: https://docs.rye.com/api-v2/api-comparison
- Crossmint — Agent Checkouts: https://www.crossmint.com/announcement/agent-checkouts
- Zinc — FAQ: https://www.zinc.com/faq
- Digital Commerce 360 — Best Buy adopts firmly: https://www.digitalcommerce360.com/2026/03/31/best-buy-firmly-agentic-commerce-platform/
- PYMNTS — Perplexity and firmly: https://www.pymnts.com/?p=2519114
- Retail Dive — Amazon tests Buy for Me: https://www.retaildive.com/news/amazon-buy-for-me-agentic-ai-thirdparty-sites/745047/
- EcommerceBytes — Buy for Me terms for brands: https://www.ecommercebytes.com/xlb8