Connect an AI agent over MCP or HTTP

402check is a plain HTTP API and an MCP server with the same seven tools. Start without a key, then pay per call.

Three steps

Call a tool over HTTP, free
No key needed: the first 10 calls a day per IP address are free on every tool except proof_create.
Request (ro_tenders)
```
curl "https://402check.com/v1/ro/tenders?q=software"
```

Add the MCP server to your agent

Streamable HTTP, stateless, POST https://402check.com/mcp. Every tool is listed with its price in the description.

Pick your client; the URL is the same everywhere.

Claude Code

claude mcp add --transport http 402check https://402check.com/mcp
# with a credits key:
claude mcp add --transport http 402check https://402check.com/mcp --header "Authorization: Bearer rk_YOUR_KEY"

Claude Desktop / claude.ai

Settings -> Connectors -> Add custom connector
Name: 402check
URL:  https://402check.com/mcp
# free tier; for a credits key use an mcp-remote bridge (verify with your client)

Codex (OpenAI) ~/.codex/config.toml

[mcp_servers.402check]
url = "https://402check.com/mcp"
# with a credits key:
# http_headers = { Authorization = "Bearer rk_YOUR_KEY" }

Cursor .cursor/mcp.json

{
  "mcpServers": {
    "402check": {
      "url": "https://402check.com/mcp"
    }
  }
}

Any MCP client (Streamable HTTP)

{
  "mcpServers": {
    "402check": {
      "url": "https://402check.com/mcp"
    }
  }
}

Generic JSON with a credits key

{
  "mcpServers": {
    "402check": {
      "url": "https://402check.com/mcp",
      "headers": {
        "Authorization": "Bearer rk_YOUR_KEY"
      }
    }
  }
}

Replace rk_YOUR_KEY with your key from /buy.

Pay when the free tier runs out
Buy $5 or $20 of credits by card and send the rk_ key as a Bearer token, over HTTP or MCP. Or let an x402 client pay each 402 in USDC on Base, over HTTP.
Request with a credits key
```
curl -H "Authorization: Bearer rk_YOUR_KEY" "https://402check.com/v1/ro/company/14399840"
```
Prices and payment options

Tools

Each page has the parameters, a live form, an example response, and the data source with its limits.

Tool	What it does	Price
`ro_company`GET /v1/ro/company/{cui}	Romanian company file by CUI: registry, VAT, address, financials.	$0.01
`ro_tenders`GET /v1/ro/tenders	Search Romanian public tenders (SEAP/SICAP) by keyword or CPV code.	$0.02
`us_court`GET /v1/us/court	Search US court dockets and opinions on CourtListener by party.	$0.02
`us_sanctions` Coming soonGET /v1/us/sanctions	Screen a person or entity against OFAC sanctions lists, fuzzy matched.	$0.01
`us_trademark`GET /v1/us/trademark	Search US trademark applications and registrations (USPTO) by wordmark.	$0.02
`proof_create`POST /v1/proof	Paid only: capture a web page as hashed, timestamped HTML and screenshot.	$0.25
`proof_get`GET /v1/proof/{id}	Fetch an earlier proof: hashes, artifact links, anchor status.	free
`balance`GET /v1/balance	Remaining credit of an rk_ credits key. Free.	free

Responses and errors

Every error is JSON with an error code. The same codes come back over MCP as tool errors.

Status	Body	Billing
`200`	Result	Charged (credits or x402); free on the free tier
`400`	invalid_query, invalid_cui, invalid_url or invalid_id, with details per field	Not charged
`401`	invalid_key: the rk_ key is unknown	Not charged
`402`	payment_required (with x402 requirements) or insufficient_credits	Not charged
`404`	not_found	Not charged
`502`	upstream_error: the data source failed	Not charged
`503`	coming_soon, index_not_ready or index_stale	Not charged

Questions

Do I need an account or an API key?

No. Without credentials every tool except proof_create runs on the free tier (10 calls a day per IP). After that, pay per call with x402 or a prepaid rk_ key.

Does MCP support x402?

Not yet. Over MCP, calls use the free tier or a credits key sent as Authorization: Bearer rk_…; x402 works on the /v1 HTTP routes.

Which responses are charged?

Only 2xx responses. Validation errors, upstream failures, not-found lookups (404) and coming-soon tools are never charged.

Where is the machine-readable description?

/openapi.json (OpenAPI 3.1, with prices in x-price-usd) for HTTP clients and /llms.txt for agents.

Three steps

Call a tool over HTTP, free

Add the MCP server to your agent

Pay when the free tier runs out

Tools

Responses and errors

Questions