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fastapi.online CEFR Level Estimator
x402
fastapi.online CEFR Level Estimator is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).
Estimates the CEFR language proficiency level (A1–C2) of a given text sample using AI inference
Price / call$0.001
Success—
StatusUnknown
How this service works
Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding & crypto utilities, date/time calculators, geo/coordinate math, math & finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.
Output
Returns an estimated CEFR proficiency level (e.g. A1, A2, B1, B2, C1, or C2) for the submitted text, likely with a confidence score or explanation indicating why the text was placed at that level based on vocabulary, syntax complexity, and other linguistic features.
Example use cases
ESL curriculum content grading
“I'm building a reading exercise for intermediate English learners — can you check the CEFR level of this passage and tell me if it's appropriate for B1 students: 'Every morning, Maria takes the bus to work. She enjoys reading the newspaper during her commute and often stops at the café near her office for a cup of coffee.'”
Language learner writing feedback
“My student submitted this essay paragraph — what CEFR level does it reflect? 'Although the consequences of climate change are widely acknowledged, many governments continue to prioritize short-term economic gains over long-term environmental policies, a contradiction that undermines global sustainability efforts.'”
Localization readability audit
“We're adapting our help docs for non-native English speakers targeting a B2 audience — can you estimate the CEFR level of this snippet so I know whether to simplify it: 'To configure your account preferences, navigate to the settings panel and select the desired notification parameters from the dropdown menu.'”
Technical details
Endpoint
POSThttps://api.fastapi.online/cefr-level-estimateWhen to prefer
Choose this endpoint when you need a lightweight, pay-per-call CEFR classification without committing to a subscription or signup. It is especially useful for edtech platforms, language learning apps, or content pipelines that need programmatic difficulty labeling of text. Prefer it over general-purpose LLM prompting when you want a structured, consistent CEFR output rather than a conversational language assessment.
Side effects
- Text too short or too ambiguous to classify accurately, resulting in a low-confidence or fallback response
- Non-linguistic or code-heavy input may produce unreliable CEFR estimates
- Text exceeding 8000 characters will be rejected by the input schema
- Network or model inference errors may return a 500 or 402 payment-required response
- If the text is in a language other than English, results may be inaccurate or undefined
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| text | string |
Tags
x402
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