Text Readability Score API POST

Readability Score is a simple tool for calculating the readability score of text. It returns the readability score based on various readability formulas.

Try it — live request, no key required

Request

POSTapi.apiverve.com/v1/readabilityscore

Verification

Format

No key required to try it. Get a key to use it in your app.

200 OK

{
  "status": "ok",
  "error": null,
  "data": {
    // Text Readability Score response payload
  }
}

About the Text Readability Score API

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.

What people use it for

Content Analysis: Use the Readability Score API to calculate the readability score of text for content analysis. Use the data to analyze language, extract insights, and improve comprehension
Language Processing: Calculate readability score by using the Readability Score API for language processing. Use the data to analyze grammar, categorize text, and enhance understanding
Content Generation: Use the Readability Score API to calculate the readability score of text for content generation. Use the data to create variations, improve readability, and enhance engagement
Text Analysis: Calculate readability score by using the Readability Score API for text analysis. Use the data to analyze language, extract insights, and improve comprehension

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON: Default REST response
XML: Markup format
YAML: Human-readable
CSV: Tabular export
GraphQL: Query language
MCP: For AI agents

View all integrations →

Questions.

Common questions about the Text Readability Score API.

Read the docs →

What does the Text Readability Score API do?

Readability Score is a simple tool for calculating the readability score of text. It returns the readability score based on various readability formulas.

How do I authenticate Text Readability Score API requests?

Pass your API key in the x-api-key header over HTTPS. One key works across all 300+ APIVerve APIs — there are no per-endpoint credentials.

How much does the Text Readability Score API cost?

Each call spends 2 credits from your shared pool. The free tier includes 200 credits every month, and paid plans add more headroom.

How fast is the Text Readability Score API?

Response time depends on the endpoint — the p50 through p99 latency for this API is published on this page. Requests are served over HTTPS through a global edge network.

What response formats does the Text Readability Score API support?

JSON by default, plus XML and YAML via the format parameter. GraphQL and an MCP interface for AI agents are available across the catalog.

What HTTP method does the Text Readability Score API use?

POST over HTTPS, following standard REST conventions with a consistent { status, error, data } response envelope.

Request parameters — POST /v1/readabilityscore

Sent as JSON in the request body. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Parameter	Type	Example	Description
`text`Required	string	`The quick brown fox jumps over the lazy dog. This sentence contains every letter of the alphabet.`	The text to calculate the readability score of

Example request

curl -X POST "https://api.apiverve.com/v1/readabilityscore" \
  -H "x-api-key: YOUR_API_KEY" \
  -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."}'

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Header	When	Value
`x-api-key`Required	Every request	Your API key. Header names are case-insensitive, so `X-API-Key` is the same header.
`Authorization`Alternate	Instead of the above	`Bearer <key>` — for clients that only expose bearer auth. Resolves to the same account and the same billing.
`content-type`Required	POST body	`application/json`

401 is the only auth verdict

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.

Response — POST /v1/readabilityscore

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

Sample response

{
  "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	`{...}`
`syllableCount`	number	`82`
`lexiconCount`	number	`49`
`sentenceCount`	number	`1`
`readability`	object	`{...}`
`fleschReadingEase`	number	`13.28`
`fleschKincaidGrade`	number	`23.6`
`gunningFog`	number	`26.95`
`colemanLiauIndex`	number	`13.19`
`smogIndex`	number	`22.08`
`automatedReadabilityIndex`	number	`27.8`
`daleChallReadabilityScore`	number	`17`
`readabilityText`	object	`{...}`
`fleschReadingEase`	string	`"very confusing"`
`daleChallReadabilityScore`	string	`"average 13th to 15th-grade (college) student"`
`averageGradeLevel`	number	`22.7`	Average grade level from all metrics
`targetAudience`	string	`"post-graduate"`	Suggested target audience based on readability

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Header	What it carries
`x-api-remaining-credits`	Credits left in the current cycle
`x-api-credits-used`	Credits spent in the current cycle
`x-api-max-credits`	The allowance for the cycle
`x-api-version`	Version of the endpoint that answered

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

Status	Meaning	What to do
`400`	Input was rejected	Read `error`; it names the parameter that has to change.
`401`	Key missing or invalid	Check the header name and the key value.
`403`	Key valid, but not permitted here	A key restriction or an IP allow-list — never a bad key.
`429`	Rate limited, or out of credits	Read `error` to tell them apart, then back off or top up.

What a call costs — 2 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Plan	Per month	Credits	Text Readability Score calls	Per 1,000 calls
Free	Free	200	100	Free
Starter	$29.99	200,000	100,000	$0.30
Pro	$99.99	1,000,000	500,000	$0.20
Mega	$299.99	4,000,000	2,000,000	$0.15

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Compare all pricing tiers →

Call it from cURL — POST /v1/readabilityscore

No SDK to install — this is a plain HTTPS call to /v1/readabilityscore with your key in the x-api-key header. Swap in a real key and it runs as-is.

cURL

1
2

curl "https://api.apiverve.com/v1/readabilityscore" \
  -H "x-api-key: YOUR_API_KEY"

Resources

GitHubapiverve/readabilityscore-apiSource, issues and the examples this page is built from.ReferenceText Readability Score API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/readabilityscorenpm APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Node.js — POST /v1/readabilityscore

Install the Node.js SDK, then call the Text Readability Score API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — npm

npm install @apiverve/readabilityscore

Node.js

const res = await fetch("https://api.apiverve.com/v1/readabilityscore", {
  headers: { "x-api-key": "YOUR_API_KEY" },
});
const { data } = await res.json();
console.log(data);

Resources

npm@apiverve/readabilityscoreThe published Node.js client, versioned and signed.GitHubapiverve/readabilityscore-apiSource, issues and the examples this page is built from.ReferenceText Readability Score API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Python — POST /v1/readabilityscore

No SDK to install — this is a plain HTTPS call to /v1/readabilityscore with your key in the x-api-key header. Swap in a real key and it runs as-is.

Python

import requests

res = requests.get(
    "https://api.apiverve.com/v1/readabilityscore",
    headers={"x-api-key": "YOUR_API_KEY"},
)
print(res.json()["data"])

Resources

Also published for

@apiverve/readabilityscorenpm APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from C# / .NET — POST /v1/readabilityscore

Install the C# / .NET SDK, then call the Text Readability Score API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — NuGet

dotnet add package APIVerve.API.TextReadabilityScore

C# / .NET

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("x-api-key", "YOUR_API_KEY");

var json = await client.GetStringAsync("https://api.apiverve.com/v1/readabilityscore");
Console.WriteLine(json);

Resources

NuGetAPIVerve.API.TextReadabilityScoreThe published C# / .NET client, versioned and signed.GitHubapiverve/readabilityscore-apiSource, issues and the examples this page is built from.ReferenceText Readability Score API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/readabilityscorenpm

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Go — POST /v1/readabilityscore

No SDK to install — this is a plain HTTPS call to /v1/readabilityscore with your key in the x-api-key header. Swap in a real key and it runs as-is.

req, _ := http.NewRequest("GET", "https://api.apiverve.com/v1/readabilityscore", nil)
req.Header.Set("x-api-key", "YOUR_API_KEY")

res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))

Resources

Also published for

@apiverve/readabilityscorenpm APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from PHP — POST /v1/readabilityscore

No SDK to install — this is a plain HTTPS call to /v1/readabilityscore with your key in the x-api-key header. Swap in a real key and it runs as-is.

PHP

$ch = curl_init("https://api.apiverve.com/v1/readabilityscore");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-api-key: YOUR_API_KEY"]);

$response = curl_exec($ch);
echo $response;

Resources

Also published for

@apiverve/readabilityscorenpm APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Ruby — POST /v1/readabilityscore

No SDK to install — this is a plain HTTPS call to /v1/readabilityscore with your key in the x-api-key header. Swap in a real key and it runs as-is.

Ruby

require "net/http"

uri = URI("https://api.apiverve.com/v1/readabilityscore")
req = Net::HTTP::Get.new(uri)
req["x-api-key"] = "YOUR_API_KEY"

res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

Resources

Also published for

@apiverve/readabilityscorenpm APIVerve.API.TextReadabilityScoreNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

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Text Readability Score API POST

Try it — live request, no key required

About the Text Readability Score API

What people use it for

Ways to call it

Other ways to use Text Readability Score

Questions.

Request parameters — POST /v1/readabilityscore

Required

Authentication

Response — POST /v1/readabilityscore

Response fields

Response headers

Errors

What a call costs — 2 credits per call

Call it from cURL — POST /v1/readabilityscore

Resources

Also published for

Call it from Node.js — POST /v1/readabilityscore

Resources

Also published for

Call it from Python — POST /v1/readabilityscore

Resources

Also published for

Call it from C# / .NET — POST /v1/readabilityscore

Resources

Also published for

Call it from Go — POST /v1/readabilityscore

Resources

Also published for

Call it from PHP — POST /v1/readabilityscore

Resources

Also published for

Call it from Ruby — POST /v1/readabilityscore

Resources

Also published for

Zero-code embed — one snippet, no backend

Changelog — Text Readability Score API

Text Processing

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