Mercapi

Let your AI assistant search Mercari, Japan's largest second-hand marketplace, in plain language — no scraping, no manual filtering. An MCP server built on mercapi.

Ask things like:

"Find a used Daiwa Saltiga reel under ¥30,000 in good condition, cheapest first."

"What's this seller's rating, and what else are they selling?"

"Any auctions ending soon for vintage Game Boy games?"

The assistant calls the tools below, gets back compact results with direct jp.mercari.com links, and reasons over them for you.

Setup

Requires Node ≥ 20.

Claude Code

claude mcp add mercari -- npx -y mercapi-mcp

Claude Desktop / Cursor — add to your mcpServers config:

{
  "mcpServers": {
    "mercari": {
      "command": "npx",
      "args": ["-y", "mercapi-mcp"]
    }
  }
}

No API key or account needed.

Tools

search_items is the workhorse. The assistant chooses:

• Filters — priceMin/priceMax (JPY), condition (brand_new → bad), status (on_sale/sold/all), excludeKeyword
• Sorting — score (default), price_asc, price_desc, newest, likes
• How much to return — limit (1–120, default 20) and detail (compact or full)
• Output format — format (text, default, or json for raw structured data)
• Pagination — pass pageToken from a previous result

All four tools accept format: "json" to return structured objects (mercapi's parsed fields) instead of human-readable text — useful for programmatic downstream use.

Auction listings are flagged with current bid count and deadline; get_item returns full auction state (starting price, highest bid, ends-at). Japanese keywords give the best results.

How it works

Results come back as compact structured text rather than raw JSON — roughly 90% fewer tokens for the same information, so the assistant can scan many listings without blowing its context. Every item includes its https://jp.mercari.com/item/{id} link so you can open anything it finds.

Notes

• Unofficial API. Requests hit Mercari's private endpoints from your own machine's IP. Fine for interactive use; heavy automated querying may get throttled.
• API health is monitored continuously upstream — status page.
• This is a read-only search tool. It cannot buy, bid, message, or list items.

Credits

Wraps mercapi (Node), itself a port of take-kun/mercapi (Python), which reverse-engineered the Mercari API.

License

MIT