address validation and normalization API

Here’s a practical design for an Address Validation and Normalization API.

What it does

The API should accept a raw address and return:

• Validated address: whether it is likely deliverable / structurally valid
• Normalized address: standardized formatting and components
• Confidence / match score
• Parsed components: street, city, state, postal code, country, etc.
• Suggestions: if the address is ambiguous or partially incorrect

---

Core endpoints

1) Validate and normalize address

POST /v1/addresses/validate

Request

{
  "address_line1": "1600 pennsylvania ave nw",
  "address_line2": "",
  "city": "washington",
  "state": "dc",
  "postal_code": "20500",
  "country": "US"
}

Response

{
  "valid": true,
  "deliverable": true,
  "confidence": 0.98,
  "normalized": {
    "address_line1": "1600 Pennsylvania Ave NW",
    "address_line2": "",
    "city": "Washington",
    "state": "DC",
    "postal_code": "20500-0003",
    "country": "US"
  },
  "components": {
    "house_number": "1600",
    "street_name": "Pennsylvania",
    "street_suffix": "Ave",
    "street_directional": "NW",
    "city": "Washington",
    "state": "DC",
    "postal_code": "20500-0003",
    "country": "US"
  },
  "warnings": [],
  "suggestions": []
}

---

2) Batch validate addresses

POST /v1/addresses/batch-validate

Request

{
  "addresses": [
    {
      "id": "1",
      "address_line1": "10 downing st",
      "city": "london",
      "postal_code": "SW1A 2AA",
      "country": "GB"
    },
    {
      "id": "2",
      "address_line1": "123 fake street",
      "city": "new york",
      "state": "ny",
      "postal_code": "10001",
      "country": "US"
    }
  ]
}

Response

{
  "results": [
    {
      "id": "1",
      "valid": true,
      "deliverable": true,
      "normalized": {
        "address_line1": "10 Downing St",
        "city": "London",
        "postal_code": "SW1A 2AA",
        "country": "GB"
      }
    },
    {
      "id": "2",
      "valid": false,
      "deliverable": false,
      "confidence": 0.12,
      "warnings": ["Street not found"]
    }
  ]
}

---

3) Parse only

POST /v1/addresses/parse

Useful when you want component extraction without external validation.

---

4) Lookup suggestions / autocomplete

GET /v1/addresses/suggest?q=1600+pen

Returns likely completions and standardized results.

---

Validation rules

A good API typically checks:

• Required fields based on country
• Postal code format and existence
• City/state consistency
• Street existence and house number plausibility
• Country-specific formatting and abbreviations
• Deliverability against address reference data
• Duplicate or ambiguous addresses

---

Normalization rules

Normalization often includes:

• Title casing names
• Expanding / standardizing street abbreviations
• Standardizing state/province codes
• Formatting postal codes
• Removing extra punctuation/spaces
• Country-specific address ordering

Examples:

• street → St
• avenue → Ave
• new york → New York
• us → US

---

Suggested response fields

Return these fields consistently:

• valid: structural correctness
• deliverable: known deliverable address
• confidence: 0 to 1 score
• normalized: canonical form
• components: parsed fields
• warnings: minor issues
• errors: blocking issues
• suggestions: alternate matches

---

Error model

Example:

{
  "error": {
    "code": "INVALID_POSTAL_CODE",
    "message": "Postal code does not match country format",
    "field": "postal_code"
  }
}

Common codes:

• MISSING_REQUIRED_FIELD
• INVALID_COUNTRY
• INVALID_POSTAL_CODE
• ADDRESS_NOT_FOUND
• AMBIGUOUS_ADDRESS
• RATE_LIMITED

---

Authentication

Use:

• API key
• OAuth2 client credentials
• JWT for internal services

Example header:

Authorization: Bearer <token>

---

Best practices

• Support country-specific schemas
• Return confidence score and candidate matches
• Keep raw input and normalized output separate
• Provide batch validation
• Add idempotency keys for retries
• Log validation outcomes for monitoring and improvement

---

If you want to build it

I can also provide any of these:

1. OpenAPI/Swagger spec
2. Database schema
3. FastAPI/Node.js implementation
4. Address normalization rules by country
5. Architecture for using Google Maps/Loqate/Melissa/Smarty APIs

If you want, I can generate a full OpenAPI 3.0 spec for this API next.