MCP server

quarry is one Model Context Protocol server, served over Streamable HTTP:

https://quarry.market/api/mcp

It works without an account. Searching the catalog and reading dataset details are free. Full, cited passages are paid per question: with your subscription when your quarry account or an API key is connected, or with an x402 payment from the agent's own wallet.

Connect a client

Any client that supports remote MCP servers over Streamable HTTP can connect. Exact setup per client, including API keys:

• Assistants: Claude, ChatGPT, Meta Muse
• Coding agents: Claude Code, Cursor, VS Code, Devin Desktop and Windsurf, Goose, OpenClaw
• Frameworks and APIs: LangChain, LlamaIndex, Vercel AI SDK, OpenAI, Anthropic, Pydantic AI, Google ADK, CrewAI, Mastra
• Platforms: Microsoft Copilot Studio, OpenAPI

Clients that use an mcpServers configuration generally accept:

{
  "mcpServers": {
    "quarry": { "type": "http", "url": "https://quarry.market/api/mcp" }
  }
}

To use your subscriptions from code that can't run a sign-in, create an API key and send it as Authorization: Bearer qk_….

Tools

Every tool has a title and read-only or destructive annotations. Calling an account tool without signing in returns HTTP 401 with an OAuth challenge (resource_metadata points to /.well-known/oauth-protected-resource/api/mcp), which clients use to start sign-in.

search

Datasets are ranked by meaning, not just keywords, across the whole catalog. Each result includes username, slug, name, description, category, score, price_usdc (null when the dataset only sells subscriptions), free (true when questions cost nothing), subscription_offer, number of documents, listed_at, content_updated_at, listing_url and endpoint.

The top five results also carry a free snippet: at most 200 characters of the best-matching passage, with its filename and page. It is a preview to judge relevance, not the answer. snippet is null when the creator turned previews off or a preview limit was reached.

ask

ask tries, in order:

0. Free datasets. A dataset priced at 0 answers without any payment or account, within rate limits.
1. Your subscription, when your account or API key is connected and has quota left for this dataset. One successful call uses one question. Pass a request_id and reuse it only to retry the identical request, so a retry is never counted twice.
2. An x402 payment sent with the call (see below).
3. Otherwise it returns isError: true with the price and how to pay.

A successful answer contains results, each with content, score and a citation: filename, page_start, page_end, heading_path, document_updated_at and listing_url. paid_with is subscription, x402 or free. Cite the file, page and listing URL. document_updated_at is when the file was last updated on quarry, not when the source was written; rely on dates stated in the passage itself when timing matters.

When ask cannot answer without payment, the second text block also carries dataset_id and, when a monthly plan exists, next: { tool: "request_subscription", dataset_id, offer_id }.

Pay per question with x402 inside MCP

quarry follows the x402 MCP transport. When ask has no payment, the result is:

• isError: true;
• structuredContent: the x402 PaymentRequired object (x402Version, resource, accepts with scheme, network, asset, amount and payTo);
• a second text block with quarry's hints (price, monthly plan, how to connect an account).

Sign a payment for one of the accepts entries with your wallet and call ask again with the identical arguments and the PaymentPayload in _meta["x402/payment"]. A settled call returns the passages and the settlement (transaction hash, payer, network) in _meta["x402/payment-response"]. A payment that is invalid, already used or refused at settlement returns PaymentRequired again with the reason in error, and no passages. You are charged only when passages are returned.

import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const payer = new x402Client();
registerExactEvmScheme(payer, { signer: privateKeyToAccount(process.env.AGENT_PRIVATE_KEY) });

const args = { username: "alice", slug: "sec-filings", query: "Which segment grew fastest?" };
const unpaid = await mcp.callTool({ name: "ask", arguments: args });
const payment = await payer.createPaymentPayload(unpaid.structuredContent);
const paid = await mcp.callTool({ name: "ask", arguments: args, _meta: { "x402/payment": payment } });

Limits

• Requests to the endpoint: 60 per minute per IP address, or per token when you send one (OAuth or API key).
• search: 20 per minute and 300 per day, per signed-in account or per IP, and a global daily ceiling for the free tier.
• Free datasets: the same per-caller limit as paid questions.
• Free snippets: 30 per day for each caller and dataset, and a per-dataset cap.
• Paid questions: 30 per minute per paying wallet or subscription.

Errors inside a tool result set isError: true and include an error object with a code and message. Check the tool result as well as the HTTP status.