foura_single
Send one HTTP request and return the response. Fastest of the four tools (typically 200ms-2s). Use for static pages, JSON APIs, server-rendered HTML. Set unblocker:true if the target has wire-level anti-bot protection. Switch to foura_proxy if you get blocked - status 403, status 429, captcha pag...
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What foura_single does on Mcp
AI agents call foura_single to retrieve information from Mcp without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
url | string | Yes | Target URL. Public hosts only - private/reserved ranges (RFC 1918 10/8, 172.16/12, 192.168/16, loopback 127/8, link-local, IPv6 ULA fc00::/7, IPv6 loopback ::1, |
data | object | — | Request body. Strings sent as-is; objects auto-serialized to JSON. Example: {"query": "hello"} for POST APIs. |
proxy | string | — | Optional proxy. Two forms: (1) URL `http://host:port` or `socks5://host:port`; (2) base36 ID from foura_proxy (e.g. `4DZ3VE`) - same exit IP. For rotation, use |
method | string | Yes | HTTP method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, or any WebDAV verb like PROPFIND/MKCOL) |
headers | array | — | Custom HTTP headers as [name, value] tuples. Example: [["Accept", "application/json"], ["Referer", "https://google.com/"]] |
validate | object | — | Post-fetch response validation. When the response fails these checks the tool returns an error envelope. |
unblocker | boolean | — | Inject realistic browser headers (User-Agent, Sec-Ch-Ua, Accept-Encoding, …) and make the request look like it's coming from a real browser at the wire level. D |
timeout_ms | integer | — | Overall request timeout in ms (max 120000, default 15000) |
tryJsonData | boolean | — | If true, attempt JSON.parse on the response body. On success, `data` is the parsed value (typically object or array). On parse failure, `data` silently stays as |
returnBuffer | boolean | — | Return raw bytes as a serialized Buffer JSON shape (`{type:"Buffer", data:[byte, ...]}`, bytes 0-255) instead of decoded string. Use for binary responses (image |
offload_large | boolean | — | If true, response bodies >= 50KB are written to disk and returned as a resource_link instead of inlined. Saves token context but requires a client that supports |
followRedirects | integer | — | Max number of redirects to follow (0-20). Omit to disable redirect following. |
Parameters from the server's own tool schema.
Why foura_single is rated Low
This tool fetches web pages and API responses via HTTP requests, which is a read/retrieval operation. It has no write or destructive side effects on its own. The medium severity reflects the potential for misuse in scraping sensitive data, bypassing anti-bot protections, or accessing restricted content behind WAFs/CAPTCHAs.
From the tool's definition Send one HTTP request and return the response. Use for static pages, JSON APIs, server-rendered HTML.
Risk signalsAccepts URL/endpoint input (url) · High parameter count (25 properties)
Attacks that exploit this kind of access
The rule that runs foura_single safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Mcp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For foura_single, this is the rule to start with:
foura_single is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Mcp, apply this rule, and every foura_single call is checked against it from then on.
Questions about foura_single
Send one HTTP request and return the response. Fastest of the four tools (typically 200ms-2s). Use for static pages, JSON APIs, server-rendered HTML. Set unblocker:true if the target has wire-level anti-bot protection. Switch to foura_proxy if you get blocked - status 403, status 429, captcha page, OR response carries x-vercel-mitigated: challenge / cf-mitigated: challenge headers, OR body title matches Vercel Security Checkpoint / Just a moment / Attention Required / We're verifying your browser. For these tier-1 WAF challenges call foura_proxy with maxTries:25-30 (the default 5 is sized for lightly-blocked sites). On success, chain the returned proxy ID into foura_browser.proxy if the page also needs JavaScript to render. It is categorised as a Read tool in the Mcp MCP Server, which means it retrieves data without modifying state.
foura_single accepts 12 parameters: url, data, proxy, method, headers, validate, unblocker, timeout_ms, tryJsonData, returnBuffer, offload_large, followRedirects. Required: url, method. The full parameter table on this page comes from the server's own tool schema.
Register the MCP server in PolicyLayer and add a rule for foura_single: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Mcp. Nothing to install.
foura_single is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the foura_single rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for foura_single. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
foura_single is provided by the MCP server (@fouradata/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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