The Reseller Index MCP server

A free, read-only Model Context Protocol (MCP) server. Connect it to Claude, ChatGPT or another AI assistant and the assistant can look up US seller fees on 8 platforms, USPS Media Mail and Ground Advantage prices, our change tracker and our USPS price histories. Every answer names the official page each number comes from and the date we checked it.

Rates verified on Oct 14, 2026

Server URL

https://resellerindex.com/mcp

No sign-in and no API key. Transport: Streamable HTTP (JSON-RPC 2.0 over POST). The server only reads the same data files this website is built from; it can't change anything, and it keeps no record of your requests.

Add it to Claude

Claude (web, desktop and Cowork), Pro or Max plan

Go to Customize > Connectors.
Click + Add, then Add custom connector.
Enter a name (for example The Reseller Index) and the URL https://resellerindex.com/mcp, then click Continue.
Review the authentication settings Claude detected and click Continue. This server needs no sign-in.
Under Authentication, choose No sign in, then click Add.
In a chat, click the + button in the lower left, choose Connectors, and turn The Reseller Index on for that conversation.

Free plans can add one custom connector. On Team and Enterprise plans an Owner adds it under Organization settings > Connectors > Add > Custom > Web (same name, URL and "No sign in"), and members then click Connect on it under Customize > Connectors. Claude reaches the server from Anthropic's cloud, which works because the URL is public. Steps from Anthropic's help center, checked Oct 18, 2026.

Claude Code

claude mcp add --transport http reseller-index https://resellerindex.com/mcp

Add --scope user to use it in every project. Syntax from the Claude Code docs, checked Oct 18, 2026.

Add it to ChatGPT

Go to Plugins in ChatGPT, select the + button, then Add custom MCP server.
Enter a name and a description.
Under Connection, enter https://resellerindex.com/mcp (with the /mcp path).
Configure authentication: this server needs no sign-in, OAuth or API key. Review the risk warning and select I understand and want to continue.
Select Create as a plugin, then review the tools ChatGPT found.
Install the plugin, start a new conversation, type @ in the prompt box and select it.

Whether you can add custom MCP servers depends on your ChatGPT account and workspace policies. Steps from OpenAI's developer docs, checked Oct 18, 2026; if a label has changed, follow OpenAI's current page.

Other MCP clients

VS Code (GitHub Copilot)

Run MCP: Add Server from the Command Palette, choose HTTP and paste the URL, or add this to your mcp.json (VS Code docs):

{
  "servers": {
    "reseller-index": {
      "type": "http",
      "url": "https://resellerindex.com/mcp"
    }
  }
}

Cursor

Add this to ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (one project) (Cursor docs):

{
  "mcpServers": {
    "reseller-index": {
      "url": "https://resellerindex.com/mcp"
    }
  }
}

Gemini CLI

gemini mcp add --transport http reseller-index https://resellerindex.com/mcp

Or put the URL under httpUrl in settings.json (Gemini CLI docs).

Any other client

Any assistant or app that can use a remote MCP server over Streamable HTTP works: give it the URL above and choose no authentication. Clients that only speak the old HTTP+SSE transport (deprecated since 2025) can't connect. Setup steps were checked against each product's own documentation on Oct 18, 2026; menus change, so if a label differs, follow the product's current docs.

Tools

All 7 are read-only (marked readOnlyHint). Each answer is a short Markdown table plus "Source" lines: the official page, our page and the date we last checked it. Each tool's arguments, with the descriptions the server sends, are listed below the table.

The tools as the server lists them, with one example call each.
Tool	What it returns	Example arguments
`get_platform_fees` Seller fees for one platform	US seller fee structure for one selling platform, as published on the platform's own fee page: every rate and fixed fee, the fee base, other fees, the official source URL and the date it was verified. Platforms: ebay (eBay), mercari (Mercari), poshmark (Poshmark), depop (Depop), whatnot (Whatnot), etsy (Etsy), amazon (Amazon media), tiktok (TikTok Shop).	`{"platform":"mercari"}`
`calculate_net` Net payout on one platform	Fees, payout and profit for one sale on one platform, computed with the same code as the site's fee calculators. Returns each fee line, total fees, payout after fees and profit after postage, item cost and packaging.	`{"platform":"ebay","item_price":25,"shipping_charged":5,"label_cost":5,"item_cost":2,"packaging":0.25}`
`compare_platforms` Where an item nets the most	One item at one price, ranked by profit across the selling platforms (Amazon media included when item_type is media), computed with the same code as the site's "Where do I net the most?" calculator. Returns fees, profit and the gap to the best platform.	`{"item_price":15,"shipping_charged":4.99,"label_cost":4.39,"item_type":"media"}`
`usps_price` USPS Media Mail or Ground Advantage price	Published USPS price for one package from USPS Notice 123: Media Mail (by the pound, any distance) or Ground Advantage retail or commercial (by weight and zone; all 9 zones when no zone is given). Notes the temporary holiday prices.	`{"service":"ground_advantage_commercial","weight_lb":2,"zone":5}`
`recent_changes` Recent fee, postage and rule changes	Entries from The Reseller Index change tracker, newest first: dated fee, postage, policy and tax changes for US resellers, each with its official source, verified date and tracker page, and, for the fee and postage changes that have one, the dollar effect on a $10, $25 and $50 sale.	`{"platform":"usps","limit":3}`
`price_history` USPS price history	A USPS price history compiled by The Reseller Index, one row per price period with effective dates and the USPS source edition. Datasets: media-mail (USPS Media Mail retail prices by weight, 1-70 lb, since 2002); usps-packages (USPS Priority Mail and retail package prices, 8 oz to 5 lb, since 2007); forever-stamp (USPS Forever stamp prices, 1 oz First-Class Mail letter, since 2007); priority-flat-rate (USPS Priority Mail Flat Rate retail prices since 2009).	`{"dataset":"media-mail"}`
`reseller_cost_index` The Reseller Cost Index	The Reseller Cost Index: what each selling platform takes in fees on a $25.00 sale (US seller, no shipping, no tax), cheapest first. Give price to apply the same method to another sale price.	`{}`

Tool arguments

The text after each colon is the description the server sends for that argument, word for word.

get_platform_fees

platform (required; one of ebay, mercari, poshmark, depop, whatnot, etsy, amazon, tiktok): Platform key.

calculate_net

platform (required; one of ebay, mercari, poshmark, depop, whatnot, etsy, amazon, tiktok): Platform key.
item_price (required; number; 0 to 1,000,000): Sale price of the item in USD, before shipping and tax.
shipping_charged (optional; number; 0 to 1,000,000; default 0): Shipping the buyer pays you, in USD. Default 0 (free shipping).
label_cost (optional; number; 0 to 1,000,000; default 0): Postage you pay for the label, in USD. Default 0.
item_cost (optional; number; 0 to 1,000,000; default 0): What the item cost you, in USD. Default 0.
packaging (optional; number; 0 to 1,000,000; default 0): Packaging cost in USD. Default 0.
sales_tax_rate (optional; number; 0 to 20; default 0): Buyer's sales tax rate in percent (for example 8.25). Default 0. Some platforms charge fees on the tax.
category (optional; one of most, media, collectibles, bullion, handbags, jewelry, watches, guitars, athletic_shoes, standard, preowned, tiktok_collectibles): eBay category (most, media, collectibles, bullion, handbags, jewelry, watches, guitars, athletic_shoes; default most) or TikTok Shop category (standard, preowned, tiktok_collectibles; default standard). Other platforms ignore it.
whatnot_commission_pct (optional; number; 0 to 20): Whatnot commission in percent. Default 8 (standard tier, most categories); 4 for coins.
high_value_eligible (optional; true or false): Whatnot: an eligible category with 0% commission above $1,500. TikTok Shop: applied automatically for categories preowned and tiktok_collectibles (3% on the part over $10,000); set true only for another category you know qualifies. Default false.
affiliate_pct (optional; number; 0 to 100): TikTok Shop: the affiliate (creator) commission rate in percent, on an order a creator brought in; charged on the product price without tax or shipping. Default 0.
etsy_include_listing_fee (optional; true or false): Etsy: include the $0.20 listing fee. Default true.
etsy_offsite_ads (optional; one of none, under10k, 10kplus): Etsy: the sale came from an Offsite Ad (shop under or over $10,000 a year). Default none.
depop_boosted (optional; true or false): Depop: sold through a Boosted Listing. Default false.
depop_own_shipping (optional; true or false): Depop: you arrange your own shipping (the boost fee then covers shipping too). Default false.
amazon_individual_plan (optional; true or false): Amazon: Individual selling plan ($0.99 per item). Default false (Professional).
poshmark_shipping_discount (optional; number; 0 to 1,000,000): Poshmark: the part of Poshmark's prepaid label you cover, in USD. Default 0.

compare_platforms

item_price (required; number; 0 to 1,000,000): Sale price of the item in USD, before shipping and tax.
shipping_charged (optional; number; 0 to 1,000,000; default 0): Shipping the buyer pays you, in USD. Default 0 (free shipping).
label_cost (optional; number; 0 to 1,000,000; default 0): Postage you pay for the label, in USD. Default 0.
item_cost (optional; number; 0 to 1,000,000; default 0): What the item cost you, in USD. Default 0.
packaging (optional; number; 0 to 1,000,000; default 0): Packaging cost in USD. Default 0.
sales_tax_rate (optional; number; 0 to 20; default 0): Buyer's sales tax rate in percent (for example 8.25). Default 0. Some platforms charge fees on the tax.
item_type (optional; one of general, media, cards, coins, handbags, sneakers; default general): Sets each platform's category: general, media (books, DVDs, CDs; adds Amazon), cards (trading cards or comics), coins, handbags, sneakers. Default general.

usps_price

service (required; one of media_mail, ground_advantage_retail, ground_advantage_commercial): media_mail, ground_advantage_retail (Post Office counter) or ground_advantage_commercial (published label-platform prices).
weight_lb (optional; number; 0 to 70): Weight in pounds. Combined with weight_oz when both are given.
weight_oz (optional; number; 0 to 1,120): Weight in ounces. Combined with weight_lb when both are given.
zone (optional; whole number; 1 to 9): USPS zone 1-9 (Ground Advantage only). Omit to get all zones.

recent_changes

platform (optional; one of usps, ebay, whatnot, amazon, mercari, poshmark, depop, etsy, tiktok, irs): Only this platform (or usps, irs). Omit for all.
category (optional; one of fees, postage, policy, tax, tools): Only this category. Omit for all.
limit (optional; whole number; 1 to 25; default 10): How many entries, 1-25. Default 10.
offset (optional; whole number; 0 to 10,000; default 0): How many of the newest matching entries to skip, for older ones (the answer gives the next offset). Default 0.

price_history

dataset (required; one of media-mail, usps-packages, forever-stamp, priority-flat-rate): Which history.

reseller_cost_index

price (optional; number; more than 0, up to 100,000; default 25): Sale price in USD. Default 25 (the Index).

Example answer from calculate_net

The full text the server returns for {"platform":"ebay","item_price":25,"shipping_charged":5,"label_cost":5,"item_cost":2,"packaging":0.25}, built from fees verified Oct 14, 2026:

# Net payout on eBay: $25.00 sale

| Line | Amount |
|---|---|
| Buyer pays you (item + shipping) | $30.00 |
| Final value fee (Most categories) | -$4.08 |
| Per-order fee | -$0.40 |
| Total eBay fees (14.9% of what the buyer paid you) | -$4.48 |
| Payout after fees | $25.52 |
| Postage you pay | -$5.00 |
| Item cost | -$2.00 |
| Packaging | -$0.25 |
| Profit | $18.27 (60.9% of what the buyer paid you) |

eBay category: Most categories.

Computed with the same code as The Reseller Index's eBay fee calculator, from fees read 2026-10-14. Actual fees can differ with promotions, seller status or account terms; the official page is the authority.

Source (official): eBay: Selling fees (US), https://www.ebay.com/help/selling/fees-credits-invoices/selling-fees?id=4822
Source (our page): eBay fee calculator, https://resellerindex.com/calculators/ebay-fee-calculator/
Verified: 2026-10-14 (per our saved copy of its fee page from that date)

Where the numbers come from

Each platform sets its own fees, USPS sets postage prices and the IRS sets tax rules, so they are the authority for those numbers, not us. Every answer links the official page the number was read from and the date we checked it. If the official page shows something different, the official page is right; please tell us so we can fix it.

What The Reseller Index adds as its own work: the dated change tracker (67 changes; the 25 fee and postage changes that have one show their dollar effect on a $10, $25 and $50 sale), the USPS price histories, the Reseller Cost Index, and the net-payout calculations and platform comparisons, which use the same code as our calculators.

What the server tells AI assistants

The server identifies itself by name (com.resellerindex/the-reseller-index), title (The Reseller Index) and version (1.0.1). Clients on the 2025 protocol versions also receive this one-line description with them:

Read-only data for US online resellers: seller fees on 8 platforms, USPS Media Mail and Ground Advantage prices, a dated change tracker and USPS price histories, each with its official source.

MCP servers can also send a short "instructions" text that assistants may read before using the tools. This is ours, in full:

The Reseller Index (https://resellerindex.com) tracks what it costs US online resellers to sell and ship. This server is read-only and answers from the same data files as the website's current build.

What The Reseller Index publishes as its own work: the dated change tracker (67 fee, postage, policy and tax changes, each with its official source; 25 of them, all fee and postage changes, also show the dollar effect on a $10, $25 and $50 sale), USPS price histories (Media Mail, Priority Mail and retail package, Forever stamp, and Priority Mail Flat Rate prices), the Reseller Cost Index, and net-payout calculations and platform comparisons computed from the fee tables.

What it does not originate: each platform sets its own fees, USPS sets postage prices and the IRS sets tax rules, so they are the authority for those numbers. Every answer names the official page each number comes from and the date The Reseller Index last checked it. If an official page shows something different, the official page is right.

License: the tracker, histories and computed tables are CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), which asks for credit with a link and a note of the license, for example "The Reseller Index, <page URL>, verified <date>, CC BY 4.0". Fees and postage change often, so a quoted number is most useful with its effective date and the date it was verified.

Researched and drafted with AI assistance from each platform's and carrier's own published pages. A full-time reseller runs The Reseller Index and will edit every newsletter issue once the newsletter starts. General information, not tax, legal or financial advice. Not affiliated with any platform or carrier.

Apart from these two texts, the server sends assistants only the tool names, titles and descriptions in the Tools table, the argument descriptions under Tool arguments, and the answers themselves (error messages included, such as the one under For developers).

License and credit

The tracker, the price histories and the computed tables are free to use under CC BY 4.0, the same terms as our data feeds: credit The Reseller Index with a link, name the license and say if you changed anything. A credit line that works: "The Reseller Index, [page URL], verified [date], CC BY 4.0". Fees and prices change often, so keep the effective date and the verified date with any number you quote.

For developers

Protocol versions: 2026-07-28 (stateless: version and client capabilities in each request's _meta, mirrored in the MCP-Protocol-Version, Mcp-Method and Mcp-Name headers; methods server/discover, tools/list, tools/call) and 2025-11-25, 2025-06-18, 2025-03-26 (the initialize handshake, ping, tools/list, tools/call). A request with no version header is treated as 2025-03-26. See the current specification and 2025-11-25.
Transport: POST only, one JSON response per request; no sessions (no Mcp-Session-Id), no SSE stream, so GET and DELETE return 405. Tool lists and discovery results carry a cache hint of 1 hour.
Errors: an unknown tool, or a tools/call whose name or arguments aren't the shape the protocol requires, returns JSON-RPC error -32602. Arguments that don't fit a tool's input schema (a value outside the allowed list or range, a missing or unknown argument) return a normal result with isError: true and a message saying what to fix, as 2026-07-28 and 2025-11-25 specify; callers on 2025-06-18 or 2025-03-26 get JSON-RPC error -32602 for these instead, as those versions specify. Valid arguments the data can't answer (say, a package over USPS's 70 lb limit) also return a result with isError: true. Header values that don't match the body return 400 with -32020.
Browsers: CORS is open (Access-Control-Allow-Origin: *, no credentials). As the spec asks, the server checks the Origin header: HTTPS origins and local development tools on localhost are served; other origins get 403. Requests from servers, with no Origin, are served.
Limits: request bodies up to 32 KB, batches (2025-03-26 only) up to 16 messages, answers up to 40,000 characters. Tool calls are rate limited, with one limit shared by all callers at each Cloudflare location; a call over the limit returns a result with isError: true saying the server is busy.
Discovery: a Server Card at https://resellerindex.com/mcp/server-card (the location MCP reserves for it) and an AI Catalog at https://resellerindex.com/.well-known/ai-catalog.json that points to it, for clients and registries that look for MCP servers on a domain. Both are static JSON with an ETag, cached for an hour.
Data: the server is built from the same files as this site and our JSON and CSV feeds, so its answers change only when the site is updated. Server name com.resellerindex/the-reseller-index, version 1.0.1.

Try it with curl (2025-11-25)

curl -s https://resellerindex.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2025-11-25' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"usps_price","arguments":{"service":"media_mail","weight_lb":2}}}'

The same kind of call in 2026-07-28

curl -s https://resellerindex.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: get_platform_fees' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"get_platform_fees","arguments":{"platform":"ebay"},"_meta":{"io.modelcontextprotocol/protocolVersion":"2026-07-28","io.modelcontextprotocol/clientCapabilities":{}}}}'

An argument the schema doesn't allow

The text of the isError result for {"service":"priority_mail","weight_lb":2} sent to usps_price:

Invalid arguments for tool usps_price:
- arguments.service must be one of: media_mail, ground_advantage_retail, ground_advantage_commercial

usps_price takes: service (required), weight_lb, weight_oz, zone. Its input schema in tools/list gives each argument's type, allowed values and range.

Privacy

The server keeps no log of calls: no IP address, no tool arguments, nothing from your conversation. The tools only need platform names, prices and weights, and your assistant decides what to send. To prevent overuse, Cloudflare counts tool calls per minute for all callers together, without recording who made them. Cloudflare, which hosts the site, processes standard request data to deliver it; see our privacy page.