crosscheck

com.crosscheckapiPublished by crosscheckapi.comOfficial publisherv0.6.0Updated Oct 25, 2026

Checks for AI agents over x402: review drafts, accept-check handoffs, scan skills before install.

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Overview

AI-generated overview

An independent review service that lets an assistant check drafts, agent handoffs and skill files before acting, paid per call in USDC over x402.

What you can do
Review drafts such as emails, reports or PR descriptions and get a pass or specific issues with fixes, optionally against the original request and sources, with a signed receipt and a free receipt verification tool. Accept-check work another agent handed back against the task before paying or passing it on. Security-review a skill or MCP server's files before install, read-only, with a free lookup of earlier scans by bundle hash. For x402 sellers, produce a dated report on a paid resource and watch it hourly for 30 days with change alerts. Retrieve the status, verdict and receipt of an earlier paid call.
When to use it
Useful when an assistant produces text a human will read and you want a second opinion on arithmetic, contradictions, placeholders, leaked secrets or prompt injection, or when you need to judge another agent's deliverable or vet a skill before installing it.
Requirements
Runs as a remote endpoint or as a local npm package via npx. Paid tools need CROSSCHECK_WALLET_KEY, the private key of a dedicated EVM wallet holding a few dollars of USDC on Base; test USDC on Base Sepolia can be used instead. Optional settings include CROSSCHECK_MAX_USD, CROSSCHECK_NETWORKS and CROSSCHECK_URL. No account or API key; network access required.
Before you install
Paid tools spend real USDC per call, roughly $0.02 to $0.06, plus $0.01 per source URL; CROSSCHECK_MAX_USD caps each check. CROSSCHECK_WALLET_KEY is a private key, so use a dedicated low-balance wallet, never a main one. Drafts are sent to the service and its review model and deleted afterwards, with only a hash kept; do not send confidential text. Sellerwatch posts alerts to a webhook or ntfy topic you configure.

Installation

In SourceWeft

  1. Open crosscheck 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.crosscheckapi%2Fcrosscheck/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": {
    "crosscheck": {
      "type": "http",
      "url": "https://crosscheckapi.com/mcp"
    }
  }
}

README

crosscheckapi

An independent second opinion on a draft before your human sees it.

Your agent sends the text it wrote: an email, report, message, PR description, or summary. crosscheck returns a JSON verdict, either pass or a list of specific issues with fixes, plus an Ed25519-signed receipt. It catches wrong arithmetic (checked in code, not by the model), contradictions, leftover placeholders, leaked secrets, unauthorized commitments, and prompt injection. Each check costs $0.02 in USDC on Base for up to 12,000 units (one per English character), paid per request over x402. There is no account and no API key.

To try it without real money, pay with test USDC on Base Sepolia (free at https://faucet.circle.com) and set CROSSCHECK_NETWORKS=eip155:84532.

MCP server

json
{  "mcpServers": {    "crosscheck": {      "command": "npx",      "args": ["-y", "crosscheckapi"],      "env": { "CROSSCHECK_WALLET_KEY": "0x<private key of a dedicated wallet>" }    }  }}

Tools:

  • quote: free. The price for a draft, and whether checks are available now.
  • order: pays the quoted price and returns the verdict and signed receipt. Pass moltbook_identity to use a free check if you are a verified Moltbook agent. Optional: request (what your human asked, word for word; the draft fails if it answers a different question or leaves part out), sources (text the draft relies on), source_urls (up to 3 pages crosscheck opens and checks the draft against, +$0.01 each), and fetch_cited (also open the draft's own links).
  • accept: pays about $0.03 and checks work another agent or service handed back against the task you gave it. Returns accept or reject with each requirement judged, before you pay for the work or pass it on.
  • skillcheck: security-checks a skill or MCP server folder before you install it. Free when someone already scanned the same files, otherwise about $0.03.
  • result: free. Status, verdict, and receipt of an earlier order.

CLI

bash
npx -p crosscheckapi crosscheck quote draft.txtnpx -p crosscheckapi crosscheck order draft.txtnpx -p crosscheckapi crosscheck accept task.txt deliverable.txtnpx -p crosscheckapi crosscheck skillcheck ./some-skillnpx -p crosscheckapi crosscheck result <job_id> <result_token>npx -p crosscheckapi crosscheck credits [wallet]npx -p crosscheckapi crosscheck order draft.txt --request "What will 12 seats cost per year?" --url https://example.com/pricing

The draft is read from the file, or from stdin if no file is given. Output is JSON.

Referrals: the paid commands (order, accept, skillcheck) take --ref <receipt hash>, the id in a crosscheck proof link (/r/<hash>) that led you here. When your wallet's first check paid in real USDC carries a ref, the wallet behind that receipt earns check credits worth 20% of what you pay for 90 days; it costs you nothing. --credits pays with your own wallet's referral credits by signing a credit order instead of paying, and falls back to USDC only when the credits do not cover the price. crosscheck credits shows your balance. The MCP tools take the same options as ref and credits, and add a free credits tool.

Settings

VariableMeaning
CROSSCHECK_WALLET_KEYPrivate key of the wallet that pays. Use a dedicated wallet holding a few dollars, never your main wallet. Only needed for paid orders.
CROSSCHECK_MAX_USDRefuse to pay more than this per check. Default 0.10.
CROSSCHECK_URLService URL. Default https://crosscheckapi.com.
CROSSCHECK_NETWORKSNetworks the client may pay on, in order of preference. Default eip155:8453,eip155:84532 (Base, then Base Sepolia). Set eip155:84532 to use test USDC only.

Receipts

Every paid check returns receipt with body, hash, and sig. The client verifies it automatically against the public key at https://crosscheckapi.com/.well-known/crosscheck-keys.json and reports receipt_check.valid. The receipt covers a SHA-256 of your draft (never the text), the payment, and a SHA-256 of the verdict, and it is chained into an append-only ledger.

Privacy

The draft is sent to crosscheck and to its review model, then deleted when the check finishes. Only its hash is kept. Do not send text your human has marked confidential.

Source, examples for Claude Code, Cursor, VS Code, OpenAI Agents SDK, LangChain, and more: https://github.com/maxugc/crosscheck

Service summary for agents: https://crosscheckapi.com/llms.txt

Source: client/README.md at commit f67118f

Tools

8

check

Review a draft

Independent review of a draft (email, report, summary, PR description) before its human sees it. Returns pass or specific issues with fixes; arithmetic is recomputed in code. With request (what the human asked), it also checks the draft answers that. With sources, each claim is checked against them and quotes are verified; with source_urls or fetch_cited, crosscheck fetches up to 3 web pages itself and checks against those (+$0.01 a page, and a dead link the draft gives fails it). $0.02. Paid per call in USDC over x402 (Base, or free test USDC on Base Sepolia). An x402-aware MCP client pays automatically: the first call returns the price as an x402 PaymentRequired error, and the retry carries the payment in _meta["x402/payment"]. Without one, use the npm client `npx -y crosscheckapi`, which pays from a wallet you set.

Parametersrefdraftrequiredrequestsourcesfetch_citedopen_reviewsource_urlsmoltbook_identity

accept

Check a deliverable against its task

Checks work another agent handed back against the task it was given, before you pay, release escrow, or pass it on. Returns accept, reject, or verify_externally with every requirement judged; counts, required JSON fields, and sums are checked in code. Optional payment_tx is verified on chain. $0.03 base. Paid per call in USDC over x402 (Base, or free test USDC on Base Sepolia). An x402-aware MCP client pays automatically: the first call returns the price as an x402 PaymentRequired error, and the retry carries the payment in _meta["x402/payment"]. Without one, use the npm client `npx -y crosscheckapi`, which pays from a wallet you set.

Parametersreftaskrequiredreferencepayment_txdeliverablerequiredpayment_network

skillcheck

Security review of a skill or MCP server

Security review of a skill or MCP server's files before you install or connect it: read, never run. Free when these exact files were scanned before (looked up by bundle hash); otherwise paid, $0.03 base. Never says safe. Paid per call in USDC over x402 (Base, or free test USDC on Base Sepolia). An x402-aware MCP client pays automatically: the first call returns the price as an x402 PaymentRequired error, and the retry carries the payment in _meta["x402/payment"]. Without one, use the npm client `npx -y crosscheckapi`, which pays from a wallet you set.

Parametersreffilesrequiredfresh

sellercheck

Check an x402 seller's resource

For x402 sellers: one dated report on your own paid resource, by code alone. Does it answer a valid 402 (v1 or v2: price, network, payTo), is it in the x402 Bazaar index, would agent402's router route to it, and how many USDC settlements reached its payTo on Base in 24 hours and 7 days. Nothing is paid to the resource. $0.05. Paid per call in USDC over x402 (Base, or free test USDC on Base Sepolia). An x402-aware MCP client pays automatically: the first call returns the price as an x402 PaymentRequired error, and the retry carries the payment in _meta["x402/payment"]. Without one, use the npm client `npx -y crosscheckapi`, which pays from a wallet you set.

Parametersmethodnetworkresourcerequired

sellerwatch

Watch an x402 resource for 30 days

For x402 sellers: sellercheck every hour for 30 days on one resource, paid once. An alert to your webhook (JSON POST) or ntfy topic only when something changes: the 402 breaks or its price or payTo change, it leaves or rejoins the Bazaar index, agent402's router flips, settlements start, double, or halve, or it is down twice in a row. Returns a public record page to link from your listing. $1. Paid per call in USDC over x402 (Base, or free test USDC on Base Sepolia). An x402-aware MCP client pays automatically: the first call returns the price as an x402 PaymentRequired error, and the retry carries the payment in _meta["x402/payment"]. Without one, use the npm client `npx -y crosscheckapi`, which pays from a wallet you set.

Parametersmethodnotifyrequirednetworkresourcerequired

skillcheck_lookup

Look up a past skillcheck

Free. The latest skillcheck of an exact bundle, by its bundle_sha256 (SHA-256 of the canonical JSON of the files sorted by path, each as {path, sha256}).

Parametersbundle_sha256required

verify_receipt

Verify a crosscheck receipt

Free. Before trusting work that arrives with a crosscheck receipt, check in code that crosscheck issued it, its signature is valid, what the outcome was, and that it covers exactly the text you were handed. Pass receipt_hash (or the receipt object) plus that text: draft, request, and sources for check, task and deliverable for accept, files for skillcheck, and the verdict if one came with it.

Parameterstaskdraftfilesreceiptrequestsourcesverdictdeliverablereceipt_hash

result

Get a result

Free. Status, verdict, and signed receipt of an earlier paid call that was still running, using the job_id and result_token it returned.

Parametersjob_idrequiredresult_tokenrequired

Version history

7
  1. v0.6.0LatestOct 25, 2026
  2. v0.5.5Sep 28, 2026
  3. v0.5.4Sep 25, 2026
  4. v0.5.3Sep 25, 2026
  5. v0.5.1Sep 25, 2026
  6. v0.2.1Sep 24, 2026
  7. v0.2.0Sep 24, 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