OpenTools
Readability Checker

Readability Checker API

Content

Analyze text readability with AI-powered insights. Get Flesch-Kincaid scores and detailed suggestions to improve content for your audience.

Authentication

All API requests require a valid API key passed in the Authorization header as a Bearer token.

Rate Limit

100 requests per minute

Endpoints

1 endpoint available

Overview

The Readability Checker API analyzes text and returns comprehensive readability metrics including Flesch Reading Ease score, Flesch-Kincaid Grade Level, and Gunning Fog Index. Perfect for content optimization, SEO analysis, and ensuring your writing matches your target audience's reading level.

What You Get

The API returns a rich set of readability metrics:

  • Basic Counts - Word count, sentence count, syllable count
  • Flesch Reading Ease - Score from 0-100 (higher = easier to read)
  • Flesch-Kincaid Grade - U.S. school grade level required to understand the text
  • Gunning Fog Index - Years of formal education needed to understand the text
  • Averages - Average words per sentence, average syllables per word
  • Difficulty Assessment - Human-readable difficulty level and grade level

Flesch Reading Ease Scale

  • 90-100 - Very Easy (5th grade)
  • 80-89 - Easy (6th grade)
  • 70-79 - Fairly Easy (7th grade)
  • 60-69 - Standard (8th-9th grade)
  • 50-59 - Fairly Difficult (10th-12th grade)
  • 30-49 - Difficult (College)
  • 0-29 - Very Difficult (College Graduate)

Use Cases

  • Content optimization for target audience reading levels
  • SEO content analysis and improvement
  • Educational content validation
  • Technical documentation accessibility checks
  • Marketing copy optimization

Endpoints

POST
/v1/tools/readability-checker
Analyze text readability and return comprehensive metrics

Request Body

Content-Type: application/json

ParameterTypeRequiredDescription
text
string
Required
The text to analyze for readability

Response Example

{
  "success": true,
  "metrics": {
    "wordCount": 156,
    "sentenceCount": 8,
    "syllableCount": 245,
    "avgWordsPerSentence": 19.5,
    "avgSyllablesPerWord": 1.57,
    "fleschReadingEase": 58.2,
    "fleschKincaidGrade": 9.4,
    "gunningFog": 12.3,
    "difficultyLevel": "Fairly Difficult",
    "readingGrade": "9th-10th Grade"
  }
}

Error Codes

400
Invalid request body or empty text
401
Missing or invalid API key
429
Rate limit exceeded
500
Internal server error

Code Examples

curl -X POST https://api.opentools.ca/v1/tools/readability-checker \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"text": "Your text content here. Add multiple sentences to get accurate readability scores."}'

Ready to get started?

Create an API key to start using the Readability Checker API.