# Readability API
> Score how easy a piece of text is to read using the standard, peer-reviewed readability formulas — Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. Pass text and get all six scores back together with the underlying counts (words, sentences, syllables, complex and polysyllabic words, letters and characters), an averaged grade level, an estimated reading time and a plain-English interpretation of the reading ease. A second endpoint counts syllables for a word or for every word in a phrase. Supply text inline via ?text=, as a query parameter or in a request body; everything is computed locally with no network calls, so it is fast and deterministic. Built for content and copywriting tools, SEO and editorial workflows, education and accessibility (plain-language) checks, and UX-writing review. A readability scorer — distinct from sentiment/NLP analysis (nlp), spelling and grammar checking (grammar), the case and text utilities (text) and string similarity (similarity). No upstream key, no cache.

## Authentication
All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys.

```bash
curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/readability-api/..."
```

## Pricing
- **Free** (Free) — 2,340 calls/Mo, 2 req/s
- **Starter** ($7/Mo) — 46,500 calls/Mo, 8 req/s
- **Pro** ($22/Mo) — 238,000 calls/Mo, 20 req/s
- **Mega** ($57/Mo) — 875,000 calls/Mo, 50 req/s

## Endpoints

### Readability

#### `GET /v1/analyze` — Readability scores for text

**Parameters:**
- `text` (query, required, string) — The text to analyse Example: `The quick brown fox jumps over the lazy dog. It was a bright cold day in April, and the clocks were striking thirteen.`

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/readability-api/v1/analyze?text=The+quick+brown+fox+jumps+over+the+lazy+dog.+It+was+a+bright+cold+day+in+April%2C+and+the+clocks+were+striking+thirteen."
```

**Response:**
```json
{
    "data": {
        "counts": {
            "words": 23,
            "letters": 93,
            "sentences": 2,
            "syllables": 28,
            "characters": 118,
            "complex_words": 0,
            "polysyllables": 0
        },
        "scores": {
            "smog_index": 3.13,
            "gunning_fog": 4.6,
            "coleman_liau_index": 5.4,
            "flesch_reading_ease": 92.17,
            "flesch_kincaid_grade": 3.26,
            "automated_readability_index": 3.36
        },
        "interpretation": "Very easy — 5th grade",
        "average_grade_level": 4,
        "reading_time_seconds": 7
    },
    "meta": {
        "timestamp": "2026-06-01T23:40:49.601Z",
        "request_id": "55b5013d-f9a1-4513-9362-13487ea17806"
    },
    "status": "ok",
    "message": "Readability analyzed",
    "success": true
}
```

#### `GET /v1/syllables` — Syllable count

**Parameters:**
- `text` (query, required, string) — A word or phrase Example: `readability scoring`

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/readability-api/v1/syllables?text=readability+scoring"
```

**Response:**
```json
{
    "data": {
        "words": [
            {
                "word": "readability",
                "syllables": 5
            },
            {
                "word": "scoring",
                "syllables": 2
            }
        ],
        "word_count": 2,
        "total_syllables": 7
    },
    "meta": {
        "timestamp": "2026-06-01T23:40:49.703Z",
        "request_id": "106e4e3b-2e55-4739-94a4-97112867643f"
    },
    "status": "ok",
    "message": "Syllables counted",
    "success": true
}
```

### Meta

#### `GET /v1/meta` — Formulas computed

**Example:**
```bash
curl -H "x-oanor-key: $KEY" \
  "https://api.oanor.com/readability-api/v1/meta"
```

**Response:**
```json
{
    "data": {
        "note": "Score how easy a piece of text is to read using the standard, peer-reviewed readability formulas. /v1/analyze?text=... returns the Flesch Reading Ease (0-100, higher is easier), the Flesch-Kincaid grade level, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index, together with the underlying counts (words, sentences, syllables, complex and polysyllabic words, letters, characters), an averaged grade level, an estimated reading time and a plain-English interpretation. /v1/syllables counts syllables for a word or every word in a phrase. Supply text via ?text=, a query parameter or a request body; everything is computed locally with no network calls. Ideal for content and copywriting tools, SEO and editorial workflows, education and accessibility (plain-language) checks, and UX-writing review. A readability scorer — distinct from sentiment/NLP (nlp), spelling and grammar (grammar), the case/text utilities (text) and string similarity (similarity). No key, no cache.",
        "formulas": [
            "Flesch Reading Ease",
            "Flesch-Kincaid Grade",
            "Gunning Fog",
            "SMOG Index",
            "Coleman-Liau Index",
            "Automated Readability Index"
        ],
        "endpoints": [
            "/v1/analyze",
            "/v1/syllables",
            "/v1/meta"
        ]
    },
    "meta": {
        "timestamp": "2026-06-01T23:40:49.800Z",
        "request_id": "f0d263e9-533b-4a0d-b77c-1704b3ff23
…(truncated, see openapi.json for full schema)
```


---
Marketplace page: https://www.oanor.com/api/readability-api
OpenAPI spec: https://www.oanor.com/api/readability-api/openapi.json