Power Pack buyer guide

Score one outreach email for $0.01 USDC on Base mainnet. Send the request without payment to receive the standard x402 challenge, authorize it with an x402-compatible client, then retry with the payment signature.

Endpoint

POST https://power-pack-x402.fly.dev/api/score-email
Content-Type: application/json

{
  "subject": "Quick question about your outbound workflow",
  "body": "I noticed your team is scaling outbound. We built a lightweight scoring step that catches weak calls to action before an email is sent. Would a 15-minute walkthrough on Tuesday be useful?",
  "recipient_context": "VP Sales at a B2B SaaS company"
}

Canonical request schema

{
  "type": "object",
  "required": [
    "subject",
    "body"
  ],
  "properties": {
    "subject": {
      "type": "string",
      "minLength": 3,
      "description": "Email subject line"
    },
    "body": {
      "type": "string",
      "minLength": 20,
      "description": "Email body copy"
    },
    "recipient_context": {
      "type": "string",
      "description": "Optional recipient role, company, or relevant context"
    }
  },
  "additionalProperties": false
}

Canonical response example

{
  "ok": true,
  "score": {
    "subject_score": 62,
    "body_score": 71,
    "predicted_open_rate_pct": 28,
    "spam_risk": 3,
    "tone": "salesy",
    "length_assessment": "too_long",
    "personalization_score": 4,
    "cta_clarity": 6,
    "top_improvements": [
      {
        "area": "subject",
        "issue": "Generic 'Quick question'",
        "fix": "Reference their specific company milestone"
      },
      {
        "area": "opening",
        "issue": "Starts with 'I hope this finds you well'",
        "fix": "Open with the prospect-specific hook"
      },
      {
        "area": "cta",
        "issue": "Vague 'let me know'",
        "fix": "Propose a specific 15-min slot"
      }
    ],
    "rewritten_subject": "Saw your Q3 launch — one idea on the onboarding flow",
    "verdict": "revise_then_send"
  }
}

Canonical response schema

{
  "type": "object",
  "required": [
    "ok",
    "score"
  ],
  "properties": {
    "ok": {
      "const": true
    },
    "score": {
      "type": "object",
      "required": [
        "subject_score",
        "body_score",
        "predicted_open_rate_pct",
        "spam_risk",
        "tone",
        "length_assessment",
        "personalization_score",
        "cta_clarity",
        "top_improvements",
        "rewritten_subject",
        "verdict"
      ],
      "properties": {
        "subject_score": {
          "type": "integer",
          "minimum": 0,
          "maximum": 100
        },
        "body_score": {
          "type": "integer",
          "minimum": 0,
          "maximum": 100
        },
        "predicted_open_rate_pct": {
          "type": "integer",
          "minimum": 0,
          "maximum": 100
        },
        "spam_risk": {
          "type": "integer",
          "minimum": 0,
          "maximum": 10
        },
        "tone": {
          "enum": [
            "professional",
            "casual",
            "aggressive",
            "friendly",
            "robotic",
            "salesy",
            "authentic"
          ]
        },
        "length_assessment": {
          "enum": [
            "too_short",
            "ideal",
            "too_long"
          ]
        },
        "personalization_score": {
          "type": "integer",
          "minimum": 0,
          "maximum": 10
        },
        "cta_clarity": {
          "type": "integer",
          "minimum": 0,
          "maximum": 10
        },
        "top_improvements": {
          "type": "array",
          "minItems": 3,
          "maxItems": 3,
          "items": {
            "type": "object",
            "required": [
              "area",
              "issue",
              "fix"
            ],
            "properties": {
              "area": {
                "enum": [
                  "subject",
                  "opening",
                  "body",
                  "cta",
                  "signoff"
                ]
              },
              "issue": {
                "type": "string"
              },
              "fix": {
                "type": "string"
              }
            },
            "additionalProperties": false
          }
        },
        "rewritten_subject": {
          "type": "string"
        },
        "verdict": {
          "enum": [
            "send_as_is",
            "revise_then_send",
            "rewrite_completely"
          ]
        }
      },
      "additionalProperties": false
    }
  },
  "additionalProperties": false
}

Exact payment terms

Home · Health · Static sample request and response · OpenAPI · x402 manifest

The live 402 challenge is authoritative. The sample does not invoke the model and is not proof of a paid result.