Medusa API + MCP vs Swell

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.

Swell

Live /:models schema with field types and descriptions for every store. One full-access secret key per environment, with no scoped or read-only key.

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

Swell

1. Call GET /:models once and cache it. It's the ground truth for custom fields
2. Check result.errors after every write. A failed validation still returns 200
3. Use $set to replace an array. A plain PUT merges arrays by element id and never shrinks them
4. Use an sk_test_ key while testing. A bare sk_ prefix is live
5. Keep expand and include small. Each level past the first three points adds rate-limit weight