Compare seller fees and profit across 12 US marketplaces before you list an item
Connects to published fee schedules for 12 US marketplaces including Amazon, Walmart, eBay and Etsy. Muse can itemize fees, net payout and profit for one item, compare marketplaces at the same price, find the price that meets a profit goal, and check item eligibility and payout timing.
Try asking Muse: "Where should I sell this jacket, and what would I actually keep after fees on eBay versus Poshmark?"
Source: Found in the official MCP Registry (io.github.davidemena-spec/marketplace-fees) · First listed November 14, 2026
Each bar is one check, every 15 minutes. Green means it answered. Last checked 2 h ago.
What Muse can see: It does not ask you to sign in, so it cannot see your accounts. It only sees what Muse sends it from your request.
Before it acts: Read what Muse plans to do before you approve it, and remove the app from Muse when you stop using it.
musedirectory.ai is not part of Meta. More about how Muse handles your information
Not in Muse's Connectors list yet, but Muse can still use it. Copy the request below and paste it into Muse. Muse asks before it shares anything with the app's site. Meta does not review apps used this way, so only use ones you trust. We tested this in the Muse app on September 24, 2026: Muse used an app's link directly this way and returned a live answer.
https://marketplace-fee-calculator-api.huggyworks.workers.dev/mcpNot in Muse's Connectors list yet. Muse can still use it: its page gives you a request to paste into Muse.
Marketplace Seller Fee Calculator is a remote MCP server, so any assistant that can add a custom connector by link can use it. Same link, same tools.
In ChatGPT, open Settings, then Connectors (called Apps & Connectors on some accounts).
Under Advanced settings, switch on Developer mode. That is what lets you add a connector by link.
Choose Create, give it a name, paste the link as the MCP server URL, and save. If it needs a sign-in, ChatGPT asks for it here.
Start a chat, open the tools menu, pick the connector, and ask. ChatGPT asks before it runs a tool the first time.
Custom connectors need a paid ChatGPT plan, and on Team, Enterprise and Edu accounts only an admin can add them. Our "Working" label means the server answered us; it cannot tell whether your plan lets you add it. All connectors that work in ChatGPT
In Claude, open Settings, then Connectors.
Choose Add custom connector, give it a name, and paste the link.
If it needs a sign-in, Claude sends you to it. Then turn the connector on in a chat from the tools menu and ask.
Custom connectors are available on paid Claude plans; on Team and Enterprise accounts an admin may need to add them. Our "Working" label means the server answered us; it cannot tell whether your plan lets you add it. All connectors that work in Claude
https://marketplace-fee-calculator-api.huggyworks.workers.dev/mcpResponse time at the last check: 143ms. Worked in 100% of checks over 30 days.
Screened, no issues found
Screening looks for known threats and hidden instructions at the time of the check, and runs again weekly and whenever the tool list changes. It cannot see the server's code, so only connect what you need and review what Muse asks to do. How screening works.
list_marketplacesList the supported US marketplaces with their valid categories, options, whether package dimensions are needed, the official fee pages used as sources and the date each was verified. Call this first to find valid category and option values.calculate_feesCalculate the seller fees, net payout, profit, margin and ROI for selling one item at a given price on one US marketplace, itemized fee by fee from the marketplace's official fee schedule. For Amazon FBA and Walmart WFS, include package dimensions to add fulfillment fees.compare_marketplacesRank every supported US marketplace (or a chosen subset) by the profit the seller keeps when selling one item at the same price. Returns the best marketplace, each marketplace's fees, payout and margin, and any marketplaces skipped or rejected with the reason.find_target_priceFind the lowest list price on each US marketplace that reaches a goal: a profit in USD, a profit margin percent, or an ROI percent. Results are sorted from cheapest required price; marketplaces where the goal can't be reached are listed with the reason.advise_marketplacesAnswer "where should I sell this?" for one item. For each US marketplace: whether it accepts the item under its published policies (prohibited and restricted items, condition rules, approval-only categories), the fees and profit at the expected price, the lowest price that meets https://marketplace-fee-calculator-api.huggyworks.workers.dev/mcpNot in Muse's Connectors list yet, but Muse can still use it. Paste this into Muse: "Use Marketplace Seller Fee Calculator to help me. It is a free service with an MCP server at https://marketplace-fee-calculator-api.huggyworks.workers.dev/mcp. It does not need an API key. Ask me before you share anything with it." Muse asks before it shares anything with the app's site. Meta does not review apps used this way, so only use ones you trust. We tested this in the Muse app on September 24, 2026: Muse used an app's link directly this way and returned a live answer.
At the last check (November 14, 2026, 14:16 UTC) the endpoint was working, answering in 143ms. Over the last 7 days it answered 100% of health checks. It is checked every 15 minutes.
It was screened on November 14, 2026 with the result "screened, no issues found". Screening checks the domain against threat feeds and reads the tools for hidden instructions and requests for passwords or card numbers. It cannot see the server's code, so grant only the access you need.
It exposes 5 tools, including list_marketplaces, calculate_fees, compare_marketplaces, find_target_price. For example, you could ask Muse: "Where should I sell this jacket, and what would I actually keep after fees on eBay versus Poshmark?"
This listing was added from public sources (Found in the official MCP Registry (io.github.davidemena-spec/marketplace-fees)). If you build Marketplace Seller Fee Calculator, claim it to correct the details and get your badge.
Paste this on your site or README. It always shows the latest check.
<a href="https://musedirectory.ai/connector/marketplace-seller-fee-calculator"><img src="https://musedirectory.ai/badge/marketplace-seller-fee-calculator.svg" alt="Marketplace Seller Fee Calculator on musedirectory.ai" width="236" height="40"></a>