SignupBouncer

Checks one email address, and optionally the signup's IP address, the way SignupBouncer checks a new signup. Returns the result as "verdict" (allow, challenge or block), a 0-100 score, the reasons with their reason codes, the normalised inbox (Gmail dots and +tags folded) and the IP's network. When the domain looks like a typo of a big mail provider (gmial.com), "suggestion" holds the corrected address. Looks up the domain's mail servers live. Every reason is listed, including ones only paid plans count. Nothing sent is stored.

{
  "type": "object",
  "properties": {
    "email": {
      "type": "string",
      "description": "The email address to check.",
      "maxLength": 320
    },
    "ip": {
      "type": "string",
      "description": "Optional IPv4 or IPv6 address the signup came from.",
      "maxLength": 64
    }
  },
  "required": [
    "email"
  ],
  "additionalProperties": false
}

{
  "type": "object",
  "properties": {
    "verdict": {
      "type": "string",
      "enum": [
        "allow",
        "challenge",
        "block"
      ]
    },
    "score": {
      "type": "number"
    },
    "reasons": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "code": {
            "type": "string"
          },
          "detail": {
            "type": "string"
          },
          "points": {
            "type": "number"
          },
          "plan": {
            "type": "string"
          }
        },
        "required": [
          "code"
        ]
      }
    },
    "normalized": {
      "type": "object"
    },
    "suggestion": {
      "type": "string",
      "description": "The corrected address when the domain looks like a typo of a big mail provider. Absent otherwise. It does not change the score."
    },
    "network": {
      "type": [
        "object",
        "null"
      ]
    },
    "data_version": {
      "type": "string"
    }
  },
  "required": [
    "verdict",
    "score",
    "reasons"
  ]
}

Explains a SignupBouncer reason code (for example disposable_domain, burner_mx, repeat_inbox, datacenter_ip): what it means, how many points it adds or whether it blocks alone, and the lowest plan on which it counts. Without a code, lists every code.

{
  "type": "object",
  "properties": {
    "code": {
      "type": "string",
      "description": "A reason code such as disposable_domain. Omit to list all codes."
    }
  },
  "additionalProperties": false
}

Says whether a domain is on SignupBouncer's disposable (burner) email list, a known relay service or a free subdomain mail service, or a known real mailbox provider, and when our harvester observed it. Uses only the loaded lists, no DNS lookup, so a brand-new burner domain on a burner mail server is caught only by check_email. Accepts a domain or an email address.

{
  "type": "object",
  "properties": {
    "domain": {
      "type": "string",
      "description": "A domain such as mailinator.com, or an email address.",
      "maxLength": 320
    }
  },
  "required": [
    "domain"
  ],
  "additionalProperties": false
}

Returns the steps and the copy-paste code that checks new signups with SignupBouncer in one stack: supabase (a hook, no code), fetch (any TypeScript server), nextjs, express, hono, python, firebase or better-auth. Use it when the user is building or changing a signup, register or auth flow. The code reads the API key from SIGNUPBOUNCER_API_KEY. The call has a 1.5-second limit, and any failure lets the signup through.

{
  "type": "object",
  "properties": {
    "stack": {
      "type": "string",
      "enum": [
        "supabase",
        "fetch",
        "nextjs",
        "express",
        "hono",
        "python",
        "firebase",
        "better-auth"
      ],
      "description": "The user's backend or auth stack."
    }
  },
  "required": [
    "stack"
  ],
  "additionalProperties": false
}

{
  "type": "object",
  "properties": {
    "stack": {
      "type": "string"
    },
    "title": {
      "type": "string"
    },
    "intro": {
      "type": "string"
    },
    "steps": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "files": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "path": {
            "type": "string"
          },
          "language": {
            "type": "string"
          },
          "code": {
            "type": "string"
          }
        },
        "required": [
          "path",
          "code"
        ]
      }
    },
    "notes": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "rules": {
      "type": "string"
    },
    "docs": {
      "type": "string"
    },
    "api": {
      "type": "string"
    }
  },
  "required": [
    "stack",
    "title",
    "steps",
    "files",
    "docs"
  ]
}