proxy_set_ja3_spoof

Enable JA3 fingerprint spoofing for HTTPS requests to bypass TLS fingerprint detection, using Chrome preset with custom user agent and host filtering.

Instructions

Legacy: enable JA3 spoofing (deprecated, use proxy_set_fingerprint_spoof). Custom JA3 strings are ignored by the curl-impersonate backend; the request will use the default Chrome preset.

Input Schema

TableJSON Schema

Name	Required	Description
`ja3`	Yes	JA3 fingerprint string (ignored by curl-impersonate backend — use proxy_set_fingerprint_spoof with a preset instead)
`user_agent`	No	User-Agent header to use with spoofed requests
`host_patterns`	No	Only spoof requests to hostnames containing these substrings. Empty = spoof all HTTPS.

Implementation Reference

src/tools/tls.ts:112-142 (handler)

The tool 'proxy_set_ja3_spoof' is registered and defined in 'src/tools/tls.ts'. It is a legacy wrapper that uses 'proxyManager.setJa3Spoof' to configure JA3 spoofing.

server.tool(
  "proxy_set_ja3_spoof",
  "Legacy: enable JA3 spoofing (deprecated, use proxy_set_fingerprint_spoof). Custom JA3 strings are ignored by the curl-impersonate backend; the request will use the default Chrome preset.",
  {
    ja3: z.string().describe("JA3 fingerprint string (ignored by curl-impersonate backend — use proxy_set_fingerprint_spoof with a preset instead)"),
    user_agent: z.string().optional().describe("User-Agent header to use with spoofed requests"),
    host_patterns: z.array(z.string()).optional().describe("Only spoof requests to hostnames containing these substrings. Empty = spoof all HTTPS."),
  },
  async ({ ja3, user_agent, host_patterns }) => {
    try {
      await proxyManager.setJa3Spoof({
        ja3,
        userAgent: user_agent,
        hostPatterns: host_patterns,
      });

      return {
        content: [{
          type: "text" as const,
          text: JSON.stringify({
            status: "success",
            message: "JA3 spoofing enabled (note: custom JA3 strings are not supported by the curl-impersonate backend; the default Chrome preset fingerprint will be used instead. Use proxy_set_fingerprint_spoof with a preset for explicit control.)",
            config: { ja3, userAgent: user_agent, hostPatterns: host_patterns ?? [] },
          }),
        }],
      };
    } catch (e) {
      return { content: [{ type: "text" as const, text: JSON.stringify({ status: "error", error: String(e) }) }] };
    }
  },
);

proxy-mcp