{"success":true,"textStats":{"wordCount":18,"sentenceCount":2,"characterCount":85,"avgSentenceLength":9,"avgSyllablesPerWord":1.56,"polysyllabicWordCount":1,"polysyllabicWordPercentage":5.6},"scores":{"fleschReadingEase":{"score":66.1,"interpretation":"Standard","suitableFor":"Age 15–17"},"fleschKincaidGrade":{"score":6.3,"interpretation":"US Grade 6 reading level"},"gunningFog":{"score":5.8,"interpretation":"Very easy"},"automatedReadabilityIndex":{"score":5.3,"interpretation":"Roughly Grade 5 reading level"},"smogIndex":{"score":6.9,"interpretation":"Grade 7 reading level","note":"SMOG is most accurate with 30+ sentences"}},"overall":{"averageGradeLevel":6.1,"verdict":"Easy read","recommendedFor":"Most adults","plainEnglishScore":70},"suggestions":["Text is short (18 words). Readability scores are most reliable with 100+ words."],"sentenceBreakdown":{"all":[{"index":1,"sentence":"The quick brown fox jumps over the lazy dog.","wordCount":9,"fre":94.3,"grade":2.3,"complexity":"Easy"},{"index":2,"sentence":"This is a simple sentence for testing readability scores.","wordCount":9,"fre":37.9,"grade":10.2,"complexity":"Hard"}],"hardest":[{"index":2,"sentence":"This is a simple sentence for testing readability scores.","wordCount":9,"fre":37.9,"grade":10.2,"complexity":"Hard"},{"index":1,"sentence":"The quick brown fox jumps over the lazy dog.","wordCount":9,"fre":94.3,"grade":2.3,"complexity":"Easy"}]}}
curl --location --request POST 'https://zylalabs.com/api/12905/user+engagement+readability+api/25687/analizar' --header 'Authorization: Bearer YOUR_API_KEY'
--data-raw '{"text": "The quick brown fox jumps over the lazy dog. This is a simple sentence for testing readability scores."}'
{"success":true,"text_a":{"fleschReadingEase":100,"gradeLevel":2.1,"verdict":"Very easy read","wordCount":11},"text_b":{"fleschReadingEase":0,"gradeLevel":19.4,"verdict":"Highly technical","wordCount":15},"comparison":{"moreReadable":"text_a","easeDifference":100,"gradeDifference":17.3,"summary":"text_a is easier to read by 100.0 Flesch points"}}
curl --location --request POST 'https://zylalabs.com/api/12905/user+engagement+readability+api/25688/comparar' --header 'Authorization: Bearer YOUR_API_KEY'
--data-raw '{"text_a": "The cat sat on the mat. It was a sunny day.", "text_b": "The feline proceeded to position itself upon the horizontal surface whilst meteorological conditions remained favourable."}'
After signing up, every developer is assigned a personal API access key, a unique combination of letters and digits provided to access to our API endpoint. To authenticate with the User Engagement Readability API simply include your bearer token in the Authorization header.
| Header | Description |
|---|---|
Authorization
|
Required
Should be Bearer access_key. See "Your API Access Key" above when you are subscribed.
|
No long-term commitment. Upgrade, downgrade, or cancel anytime. Free Trial includes up to 50 requests.
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## What it does
Score the readability of any English text or URL. Returns 5 industry-standard readability scores, actionable plain-English suggestions, sentence-level breakdown with the hardest sentences flagged, and optional target grade pass/fail.
## Scores returned
- **Flesch Reading Ease** — 0–100. Higher = easier to read.
- **Flesch-Kincaid Grade** — US school grade equivalent.
- **Gunning Fog Index** — Years of education needed to understand.
- **Automated Readability Index (ARI)** — Grade level via character/word ratio.
- **SMOG Index** — Grade level via polysyllabic word density.
## Use cases
Content teams, legal/compliance, EdTech, SEO tools, CMS pipelines, A/B copy testing.
## Endpoints
- `POST /api/analyze` — analyse text or a URL, with optional target grade
- `POST /api/compare` — compare two texts side by side
The `POST /api/analyze` endpoint returns readability scores, suggestions, sentence breakdowns, and an optional target grade result for a given text or URL. The `POST /api/compare` endpoint provides a side-by-side comparison of two texts, including their Flesch scores, grade levels, and a summary of which text is easier to read.
Key fields in the `analyze` response include `textStats` (word, sentence, and character counts), `scores` (various readability metrics), `overall` (average grade level and verdict), `suggestions`, and `sentenceBreakdown`. The `compare` response includes `text_a` and `text_b` fields with their respective scores and a `comparison` summary.
The `POST /api/analyze` endpoint accepts parameters such as `text` (the content to analyze), `url` (the URL to fetch and analyze), and an optional `targetGrade` for pass/fail evaluation. The `POST /api/compare` endpoint requires two texts to compare.
The response data is structured in JSON format. For `analyze`, it includes sections for text statistics, readability scores, overall assessment, suggestions, and sentence breakdown. For `compare`, it presents separate sections for each text's scores and a summary of the comparison.
Typical use cases include content creation for readability optimization, legal document simplification, educational material assessment, SEO content evaluation, and A/B testing for marketing copy. The API helps ensure that content is accessible to the intended audience.
Users can leverage the readability scores to adjust content complexity based on target audiences. Suggestions can guide revisions, while sentence breakdowns help identify complex sentences that may need simplification. The comparison feature aids in selecting the more readable option between two texts.
The API utilizes established readability formulas, ensuring consistent scoring based on linguistic principles. Regular updates and testing against diverse text samples help maintain accuracy and reliability in the scores provided.
Users can expect scores to range from 0 to 100 for Flesch Reading Ease, with higher scores indicating easier readability. Grade levels typically align with U.S. school grades, and suggestions often highlight areas for improvement, especially for shorter texts.
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