The Sentence Structure Evaluator assesses the complexity of sentence structure in informational texts relative to a specified grade level. It:
Identifies sentence features in the text, including sentence type composition, average words per sentence, subordinate clause ratios, and concepts per sentence.
Assigns an overall complexity rating using an LLM, combined with statistical thresholds for sentence features.
Other configurations will produce different results and may have lower accuracy. The evaluator must be run in two stages — combining them into a single step reduces accuracy.
This evaluator returns one of the following ratings, along with reasoning for you to use to determine your best course of action. Complexity ratings are relative to the target grade level you provide.
Rating
Meaning
Slightly complex
Mainly simple, short sentences with very low subordination. In Grades 3–4, no advanced complex sentences are present.
Moderately complex
A mix of simple and compound sentences with some complex constructions. In Grades 3–4, sentence length and subordination fall within moderate ranges. In Grades 5–12, no more than two advanced complex sentences.
Very complex
Longer, more elaborate sentences with multiple clauses and high subordination. In Grades 5–12, three or more advanced complex sentences are present.
Exceedingly complex
Dense, intricate sentences with a high degree of subordination; sentences often contain multiple concepts. In Grades 5–12, 65% or more of sentences are advanced complex sentences.
This evaluator is provided as Early access. Comprehensive accuracy measures are not yet available. Validation testing is ongoing.
We assessed performance on an expert-annotated dataset of ~480 texts for Grade 3 and ~480 texts for Grade 4. Accuracy has been most extensively validated on Grades 3–4. We are still evaluating the performance for grades 5-12. For more information, see Accuracy.
Metric
Result
53% agreement for Grade 3 54% agreement for Grade 4
