Calculate processor fees, invoice totals, discounts, prorations and payment plans for your business.
Helps merchants and small business owners compute payment processor fees (Stripe, PayPal, Square, Shopify), invoice totals with tax and discounts, stacked discounts, prorated charges for partial billing periods, and installment payment schedules. Three tools are free; three require a license.
Try asking Muse: "How much will I net after Stripe fees if I charge $1000 across 10 transactions?"
Source: Found in the official MCP Registry (com.moltlinestudio/merchant) · First listed September 24, 2026
Each bar is one check, every 15 minutes. Green means it answered. Last checked 4 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://mcp.moltlinestudio.com/merchantNot in Muse's Connectors list yet. Muse can still use it: its page gives you a request to paste into Muse.
Moltline Merchant Maths 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://mcp.moltlinestudio.com/merchantResponse time at the last check: 551ms. Worked in 99.1% 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.
processor_feesBreak down payment-processor fees: fee, net, and effective rate. FREE. Uses editable presets for stripe/paypal/square/shopify (verify current rates) or your own custom_pct + custom_fixed. Typical input {"amount": 1000, "processor": "stripe", "transactions": 10} returns {"gross": charge_to_netCompute the gross price to charge so you net a target after fees. FREE. 'Charge X to receive Y' after percentage + fixed processor fees. Typical input {"net_target": 100, "pct_fee": 2.9, "fixed_fee": 0.30} returns {"charge": 103.4, "fee": 3.4, "net": 100.0}. The inverse of procesinvoice_totalTotal an invoice: per-line totals, subtotal, discount, tax, grand total. FREE. Typical input {"line_items": [{"desc": "Design", "qty": 2, "unit_price": 50}], "tax_pct": 8.5, "discount_pct": 10} returns {"lines": [{"desc": "Design", "qty": 2, "unit_price": 50, "line_total": 100.0}discount_stackStack discounts correctly: sequential vs additive comparison. PREMIUM (license). The two methods differ: this shows both, the final price, and the true total discount. Typical input {"price": 200, "discounts_pct": [20, 10]} returns {"original": 200, "sequential_price": 144.0, "seprorationCompute a prorated charge or refund for a partial billing period. PREMIUM (license). Typical input {"amount_per_period": 90, "days_used": 10, "days_in_period": 30} returns {"days_used": 10, "days_in_period": 30, "prorated_charge": 30.0, "prorated_refund": 60.0, "answer": 30.0}. Uinstallment_planSplit a total into an installment schedule with optional deposit. PREMIUM (license). Rounding remainders land on the final payment so the schedule always sums exactly. Typical input {"total": 1000, "installments": 3, "deposit_pct": 10} returns {"deposit": 100.0, "payments": [300.https://mcp.moltlinestudio.com/merchantNot in Muse's Connectors list yet, but Muse can still use it. Paste this into Muse: "Use Moltline Merchant Maths to help me. It is a free service with an MCP server at https://mcp.moltlinestudio.com/merchant. 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 13, 2026, 10:45 UTC) the endpoint was working, answering in 551ms. Over the last 7 days it answered 100% of health checks. It is checked every 15 minutes.
It was screened on September 24, 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 6 tools, including processor_fees, charge_to_net, invoice_total, discount_stack. For example, you could ask Muse: "How much will I net after Stripe fees if I charge $1000 across 10 transactions?"
This listing was added from public sources (Found in the official MCP Registry (com.moltlinestudio/merchant)). If you build Moltline Merchant Maths, 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/moltline-merchant-maths"><img src="https://musedirectory.ai/badge/moltline-merchant-maths.svg" alt="Moltline Merchant Maths on musedirectory.ai" width="236" height="40"></a>