Medusa API + MCP vs Spree Commerce

Medusa API + MCP

MIT core you can self-host, with Medusa Cloud running the same APIs and no GMV fee. The official MCP server is docs-only and limited to Cloud accounts.

Spree Commerce

A self-hosted BSD 3-Clause platform with public OpenAPI files for the Store and Admin APIs, scoped secret keys, documented rate limits and idempotency keys on cart and checkout calls. GitHub lists six security advisories between January and July 2026, four rated High, and the default docs describe the 6.0 release candidate while 5.6.1 is the stable release.

Medusa API + MCP

1. Send x-publishable-api-key on every /store call. It decides which sales channels and products the agent sees
2. Ask for only the fields you need with fields. Store routes reject relations nested more than three deep since 2.20.0
3. Read the store's regions before creating a cart, since prices and shipping options depend on region
4. Place the order with POST /store/carts/{id}/complete after shipping and payment sessions are set
5. Read the release notes before upgrading a minor version. Breaking changes land there

Spree Commerce

1. Send a publishable key in X-Spree-Api-Key on every Store API call. Add X-Spree-Token with the cart token for guest carts, or a customer JWT as a Bearer token
2. Send Idempotency-Key with the cart token or a customer JWT on cart, payment and completion calls. A request carrying only the publishable key is never cached
3. Ask for fields and expand explicitly. Relations are left out by default and limit stops at 100
4. Use a secret key with the narrowest scopes for the Admin API. read_all gives a read-only key, and the CLI's auto-minted local key is read-only
5. Read the docs under /docs/v5 for a 5.6 store. The default docs describe 6.0, which renames shipments to fulfilments and splits carts from orders