Username Inspector

com.usernameinspectorPublished by usernameinspector.comOfficial publisherv1.1.0Updated Oct 24, 2026

Look up username availability on 12 resale platforms (links where blocked); compare seller fees.

VerifiedStreamable HTTPWeb executableWeb Search & ScrapingBusiness & Commerce

Overview

AI-generated overview

A free remote MCP server that lets an assistant check whether a username is free on 12 resale marketplaces and compare seller fees across 7 platforms.

What you can do
Check one username's availability across up to 12 resale platforms, returning available, taken, unverified or error per platform with profile links where useful (check_username). Build public profile page addresses for a username without contacting any marketplace, on the links-only endpoint (get_profile_links). Compare fees and net payout on seven platforms for a given USD sale price, with optional shipping and item cost inputs, ranked best first with profit, margin and ROI (compare_fees).
When to use it
Useful when picking a store or username for resale selling and wanting a quick cross-platform availability check, or when pricing an item and comparing what each marketplace keeps after fees for US sellers.
Requirements
Remote Streamable HTTP endpoint; no account or API key. Add the hosted URL in a client that supports remote servers. Self-hosting needs Node 18 or newer and serves the endpoints locally.
Before you install
The assistant sends the username to the server, which then queries the marketplaces; the README says nothing is stored and only counts are logged. Lookups are plain page requests, not official APIs, and several platforms block them, returning unverified. Fee figures are US estimates excluding sales tax and change often, so verify against the platform's own fee page before pricing. Read-only tools; no writes or payments.

Installation

In SourceWeft

  1. Open Username Inspector in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/com.usernameinspector%2Fusername-inspector/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "username-inspector": {
      "type": "http",
      "url": "https://usernameinspector.com/api/mcp"
    }
  }
}

README

Username Inspector MCP server

[Tests] [VerifyMCP trust score for Username Inspector]

A free Model Context Protocol server for people who sell on resale marketplaces. It lets an AI assistant:

  • look up whether a username or store name is free on eBay, eBay Store, Poshmark, Grailed, Vinted, Whatnot, Bonanza, Chairish, Depop, Etsy, Mercari, and Ruby Lane, and
  • compare what a sale pays out after fees on eBay, Poshmark, Mercari, Depop, Etsy, Grailed, and Vinted.

It is the code behind Username Inspector. Documentation for end users is at https://usernameinspector.com/mcp/.

Use the hosted servers

No account, no API key.

ServerURLTools
Lookupshttps://usernameinspector.com/api/mcpcheck_username, compare_fees
Links onlyhttps://usernameinspector.com/api/mcp-linksget_profile_links, compare_fees

The links-only server never contacts a marketplace. It builds the public profile page address for a username and leaves it to you to open it.

Claude Code

claude mcp add --transport http username-inspector https://usernameinspector.com/api/mcp

Clients with a JSON config (Cursor and others)

json
{  "mcpServers": {    "username-inspector": {      "url": "https://usernameinspector.com/api/mcp"    }  }}

Clients with a custom connector or remote server option: add a server and paste the URL.

It is also listed in the official MCP Registry as com.usernameinspector/username-inspector.

Tools

check_username

Looks up one username on up to 12 platforms. Each platform comes back as available, taken, unverified, or error, with a link to the profile page where one helps.

  • username (required): 3 to 50 letters, numbers, hyphens, or underscores.
  • platforms (optional): list of platform ids. Defaults to all twelve: ebay, ebaystore, poshmark, grailed, vinted, whatnot, bonanza, chairish, depop, etsy, mercari, rubylane.

Depop, Etsy, Mercari, and Ruby Lane block automated checks, so they always return a profile link. Poshmark, Vinted, and Bonanza usually return a live answer. eBay, eBay Store, Grailed, Whatnot, and Chairish often block automated lookups, and those come back as unverified with a link to check by hand. Which platforms answer can change at any time.

get_profile_links (links-only server)

Builds the public profile page address for a username on each platform. Makes no requests to any marketplace.

compare_fees

Takes a sale price in USD and, optionally, shipping_charged, item_cost, shipping_cost, and ebay_promoted_rate_percent. Returns fees and what you keep on seven platforms, best first, plus profit, margin, and ROI when costs are given. Estimates for US sellers, excluding sales tax, with the date each rate was last verified.

All tools are read-only and declare output schemas.

Limits and behavior

  • About 12 tool calls per minute per client (HTTP 429 with Retry-After beyond that), 16 KB request bodies, 5 messages per batch.
  • One username per check_username call. Results are cached in memory for 5 minutes per username and platform, and errors are never cached.
  • Outbound lookups run at most 12 at a time per instance, with a 5 second timeout per platform and 9 seconds per call.
  • Setting MCP_DISABLED=1 turns both endpoints off. MCP_LINKS_DISABLED=1 turns off only the links endpoint.

The in-process limits are per instance and best effort. On a serverless host, add a rate-limit rule at the platform level too.

Privacy

The assistant sends the username to the server, which looks it up on the marketplace and returns the result. Nothing is stored. The only logs are counts: tool name, how many platforms, and how long it took. Never usernames or IP addresses. See the privacy policy.

How the lookups work

check_username makes the same plain HTTPS request a browser makes when you open a profile page, and reads the response status or a marker on the page to tell whether a profile exists. It uses no marketplace API and no login, and it does not try to get around bot protection: when a platform answers with a challenge or an error, the result is unverified, never a guess.

Platforms can change or block these requests whenever they like. If you run this yourself, you are responsible for the load you put on those sites and for following their terms.

Run it yourself

Requires Node 18 or newer.

npm installnpm start

This serves http://127.0.0.1:3000/api/mcp and http://127.0.0.1:3000/api/mcp-links (set PORT and HOST to change that). The api/ folder is also laid out as Vercel serverless functions, so it deploys there unchanged. Use the Streamable HTTP transport; the server is stateless.

Quick check:

curl -s -X POST http://127.0.0.1:3000/api/mcp \  -H "Content-Type: application/json" \  -H "Accept: application/json, text/event-stream" \  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

Tests

npm test

The tests use Node's built-in runner and stub the network, so they make no requests to any marketplace.

Fee rates

All rates live in lib/fee-calc.js, each with a lastVerified date. They are US rates and change often, so check the platform's own fee page before pricing something.

Layout

PathWhat it does
api/mcp.js, api/mcp-links.jsThe two endpoints
lib/mcp-handler.jsHTTP front door: CORS, limits, kill switch
lib/mcp-server.js, lib/mcp-links-server.jsThe tools
lib/platform-checks.jsHow each platform is looked up
lib/fee-calc.jsFee math
lib/mcp-guard.jsRate limiter, cache, concurrency cap
server.jsLocal runner

License

MIT. See LICENSE.

Contact

Found a wrong result or want a platform added? Use the contact page.

Source: README.md at commit 7e1a4c5

Tools

2

check_username

Check username availability

Check if ONE username is free on 12 resale platforms. Example: username='vintage_finds' returns available, taken, or unverified per platform.

Parametersusernamerequiredplatforms

compare_fees

Compare reseller selling fees

Compare what a US sale keeps after fees on 7 platforms. Example: price=45, item_cost=12 ranks platforms by profit.

Parameterspricerequireditem_costshipping_costshipping_chargedebay_promoted_rate_percent

Version history

2
  1. v1.1.0LatestOct 10, 2026
  2. v1.0.0Oct 10, 2026

Score

100% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts