Overview
Readability Score works by analyzing the text provided and calculating the readability score. It uses advanced algorithms to calculate the readability score based on various readability formulas and returns the readability score.
Live Test Text Readability Score API →
Endpoint
One host, one path per API. The block below shows this call in four languages; every one of them is the same HTTP request. Making requests covers the timeouts, retries and parameter rules that apply to all of them. The SDKs wrap the same call in a typed client.
curl -X POST https://api.apiverve.com/v1/readabilityscore \
-H "x-api-key: your_api_key_here" \
-H "Content-Type: application/json" \
-d '{
"text": "Western astrology is founded on the movements and relative positions of celestial bodies such as the Sun, Moon and planets, which are analysed by their movement through signs of the zodiac (twelve spatial divisions of the ecliptic) and by their aspects (based on geometric angles) relative to one another."
}'const res = await fetch('https://api.apiverve.com/v1/readabilityscore', {
method: 'POST',
headers: {
'x-api-key': 'your_api_key_here',
'Content-Type': 'application/json',
},
body: JSON.stringify({
"text": "Western astrology is founded on the movements and relative positions of celestial bodies such as the Sun, Moon and planets, which are analysed by their movement through signs of the zodiac (twelve spatial divisions of the ecliptic) and by their aspects (based on geometric angles) relative to one another."
}),
});
if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);
const { data } = await res.json();
console.log(data);import requests
res = requests.post(
"https://api.apiverve.com/v1/readabilityscore",
headers={"x-api-key": "your_api_key_here"},
json={
"text": "Western astrology is founded on the movements and relative positions of celestial bodies such as the Sun, Moon and planets, which are analysed by their movement through signs of the zodiac (twelve spatial divisions of the ecliptic) and by their aspects (based on geometric angles) relative to one another."
},
timeout=15,
)
res.raise_for_status()
print(res.json()["data"])package main
import (
"fmt"
"io"
"net/http"
"strings"
)
func main() {
body := strings.NewReader(`{
"text": "Western astrology is founded on the movements and relative positions of celestial bodies such as the Sun, Moon and planets, which are analysed by their movement through signs of the zodiac (twelve spatial divisions of the ecliptic) and by their aspects (based on geometric angles) relative to one another."
}`)
req, _ := http.NewRequest("POST", "https://api.apiverve.com/v1/readabilityscore", body)
req.Header.Set("Content-Type", "application/json")
req.Header.Set("x-api-key", "your_api_key_here")
res, err := http.DefaultClient.Do(req)
if err != nil {
panic(err)
}
defer res.Body.Close()
out, _ := io.ReadAll(res.Body)
fmt.Println(string(out))
}Replace your_api_key_here with the key from your dashboard. When the inputs arrive as a list rather than one at a time, batch requests run up to 200 of them through this same API in a single call.
Authentication
Send your key in the x-api-key header. That is the only auth step — there is no token exchange and no per-endpoint scope to configure. Authentication covers creating, rotating and revoking keys.
A 401 means the key is missing, invalid or expired. A 403 means the key is valid but not permitted here — blocked by a key restriction or an IP allow-list. Running out of credits is a 429.
Parameters
Sent as JSON in the request body. Premium parameters are accepted on every plan but only take effect on plans that include them.
| Parameter | Type | Description |
|---|---|---|
textRequired | string | The text to calculate the readability score of |
Response
Every API returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape. Response format covers the envelope, the other output formats and how premium fields are withheld.
{
"status": "ok",
"error": null,
"data": {
"textCounts": {
"syllableCount": 82,
"lexiconCount": 49,
"sentenceCount": 1
},
"readability": {
"fleschReadingEase": 13.28,
"fleschKincaidGrade": 23.6,
"gunningFog": 26.95,
"colemanLiauIndex": 13.19,
"smogIndex": 22.08,
"automatedReadabilityIndex": 27.8,
"daleChallReadabilityScore": 17
},
"readabilityText": {
"fleschReadingEase": "very confusing",
"daleChallReadabilityScore": "average 13th to 15th-grade (college) student"
},
"averageGradeLevel": 22.7,
"targetAudience": "post-graduate"
}
}
Response fields
Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.
| Field | Type | Example | Description |
|---|---|---|---|
textCounts | object | {...} | Counts of syllables, words, and sentences found in the analyzed text |
syllableCount | number | 82 | Total number of syllables detected in the text |
lexiconCount | number | 49 | Total number of words in the text |
sentenceCount | number | 1 | Total number of sentences detected in the text |
readability | object | {...} | Raw numeric scores from each readability formula |
fleschReadingEase | number | 13.28 | Flesch Reading Ease score on a 0-100 scale; higher scores mean the text is easier to read |
fleschKincaidGrade | number | 23.6 | Flesch-Kincaid Grade Level; the approximate U.S. school grade a reader needs to understand the text |
gunningFog | number | 26.95 | Gunning Fog index; the estimated years of formal education a reader needs to understand the text on a first reading |
colemanLiauIndex | number | 13.19 | Coleman-Liau Index; an estimated U.S. grade level based on characters per word and words per sentence |
smogIndex | number | 22.08 | SMOG Index; the estimated years of education needed to understand the text, based on its count of polysyllabic words |
automatedReadabilityIndex | number | 27.8 | Automated Readability Index; an estimated U.S. grade level based on characters per word and words per sentence |
daleChallReadabilityScore | number | 17 | New Dale-Chall score; a readability rating based on how many words in the text are outside a list of words familiar to average 4th-grade readers |
readabilityText | object | {...} | Plain-language interpretations of the numeric readability scores |
fleschReadingEase | string | "very confusing" | Plain-language difficulty label derived from the Flesch Reading Ease score, e.g. "very easy" or "very confusing" |
daleChallReadabilityScore | string | "average 13th to 15th-grade (college) student" | Plain-language grade-level description derived from the Dale-Chall score, e.g. "average 4th-grade student or lower" |
averageGradeLevel | number | 22.7 | Average grade level computed by averaging the grade-based metrics (Flesch-Kincaid, Gunning Fog, Coleman-Liau, SMOG, and Automated Readability Index) |
targetAudience | string | "post-graduate" | Suggested target audience derived from the average grade level, e.g. "elementary", "high school", or "post-graduate" |
Errors
Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change. Error handling covers the full status list and which of them are worth retrying.
| Status | Meaning | What to do |
|---|---|---|
400 | Input was rejected | Read error; it names the parameter. |
401 | Key missing or invalid | Check the header name and the key value. |
403 | Key valid, but not permitted | A key restriction or IP allow-list; see key scoping. |
429 | Rate limited, or out of credits | Read error to tell them apart; see rate limits. |
Use cases
- Editorial CMS Publishing
- Before publishing articles, newsroom CMS editors check the Flesch-Kincaid grade level and word counts to match target reader expectations.
- Patient Instructions Review
- When clinicians draft care summaries, health portals flag passages scoring above an elementary target audience so staff can rephrase dense medical terms.
- Curriculum Reading Assessment
- To assign books to suitable grade bands, edtech apps evaluate uploaded chapters against Dale-Chall scores and the average grade level.
- Consumer Contract Auditing
- Flag convoluted policy clauses during drafting by checking consumer agreements against the Gunning Fog index and reading ease ratings.
Other ways to use Text Readability Score
Set up Text Readability Score on APIVerve, or reach the same source a different way. Your APIVerve account and credits work on all of them — one key, one balance.
Related
More in Text Processing: