Developers
Pump artifacts, manifests and MCP connector setup.
Amazon FBA is active. Other marketplace modules stay marked as planned until audited.
Use Margin Ruler in Claude, ChatGPT and other AI assistants (MCP)
Margin Ruler's seller calculators are also available as a remote MCP server, so an AI assistant can run them and show the result in the conversation.
Connect
- Server URL:
https://marginruler.com/mcp(Streamable HTTP, JSON-RPC 2.0). - Claude: add Margin Ruler from the Connectors Directory, or open Settings, then Connectors, then Add custom connector, and paste the URL.
- Other MCP clients (Claude Code, Cursor, VS Code, Codex): add a remote HTTP MCP server with the same URL.
Plans and sign-in
Free. No account, sign-in or API key. Every tool is a read-only calculation: it changes nothing and does not store your inputs.
Tools
- Ecommerce Return Cost Calculator
return-cost-calculator - Product Margin Leak Calculator
margin-leak-calculator - Shipping Overpay Calculator
shipping-overpay-calculator - Amazon FBA Profit Calculator
fba-profit-calculator - Break-Even Ad Spend Calculator
break-even-ad-spend-calculator - Inventory Carrying Cost Calculator
inventory-carrying-cost-calculator
Limits and troubleshooting
Public requests are rate-limited per IP address and by a daily ceiling; if a call returns "Rate limited", wait a minute and try again. Invalid inputs return an error that names the field. Results are planning estimates; each one links to the matching calculator page on Margin Ruler, where you can adjust the inputs. Margin Ruler is intended for sellers in the United States, Canada, Australia and New Zealand.
Privacy and support
How MCP calls are processed: Privacy policy. Bug reports and corrections: admin@marginruler.com.