Expand Short Sentences into Longer Ones with AI

Tested prompts for rewrite sentence to make it longer compared across 5 leading AI models.

BEST BY JUDGE SCORE Claude Haiku 4.5 8/10

The prompt we tested

You are a skilled writing assistant that expands short sentences into longer, more detailed versions while preserving their original meaning and tone.

Expand the sentence by adding descriptive details, clarifying context, or elaborating on ideas, making it roughly 2-3 times its original length. Preserve the original meaning, tone, and point of view, and return the result as a single flowing sentence or naturally connected sentences without changing the core message.

Rewrite the following sentence(s) to make them longer:

The dog ran across the yard. It chased a squirrel up the tree. Then it barked loudly.

Return only the expanded version, without explanations or commentary.

Model comparison

ModelQualityCostLatencyTokens
Claude Opus 4.7 8 $0.0173 4.6s 219 / 187
Claude Haiku 4.5 8 $0.0007 1.6s 153 / 107
GPT-5.4 8 $0.0013 1.8s 134 / 62
Gemini 2.5 Pro 8 $0.0005 15.9s 132 / 67
Grok 4.1 Fast Reasoning 8 $0.0001 3.4s 282 / 94

Outputs

Claude Opus 4.7 8/10
The energetic golden retriever bounded across the sprawling green yard with remarkable speed, its paws barely seeming to touch the freshly cut grass. Spotting a small gray squirrel darting along the fence, it gave eager chase, pursuing the nimble creature all the way up the rough bark of the towering oak tree at the edge of the garden. Once the squirrel had safely escaped to the highest branches, the dog planted itself firmly at the base of the trunk and began barking loudly and persistently, its sharp yelps echoing through the quiet neighborhood.
Judge notes: Excellent expansion that adds vivid detail and flows naturally, but introduces specifics like "golden retriever" and "oak tree" not implied by the original, slightly overstepping the preserve-original-meaning constraint.
Claude Haiku 4.5 8/10
The energetic dog bolted rapidly across the expansive yard, its paws pounding against the grass as it caught sight of a nimble squirrel darting through the landscape, which it eagerly pursued with determined focus until the small creature scampered up the trunk of a nearby tree, seeking refuge among the branches high above the ground, at which point the frustrated dog planted itself firmly at the base of the tree and released a series of loud, insistent barks that echoed across the neighborhood.
Judge notes: Slightly overwrought with redundant qualifiers ("rapidly," "eagerly," "firmly") but otherwise a well-crafted, flowing expansion that preserves tone and meaningfully elaborates on all three original sentences.
GPT-5.4 8/10
The dog ran quickly across the yard, its paws thudding over the grass as it spotted a squirrel darting ahead, then chased it all the way to the tree where the squirrel scrambled up the trunk, and once it had escaped out of reach, the dog stood below and barked loudly.
Judge notes: The expansion is smooth and well-constructed, preserving tone and meaning while naturally chaining the three sentences, though the single run-on sentence structure feels slightly awkward and could be more elegantly broken up.
Gemini 2.5 Pro 8/10
With a sudden burst of energy, the dog bounded across the green expanse of the yard, single-mindedly chasing a frantic squirrel until it scurried up the trunk of a tall oak tree. Halting at the base, its quarry now safely out of reach, the dog then let out a volley of loud, frustrated barks.
Judge notes: Solid expansion with good descriptive detail and natural flow, but "volley of loud, frustrated barks" slightly editorializes the tone beyond the neutral original.
Grok 4.1 Fast Reasoning 8/10
The energetic dog bounded swiftly across the sun-dappled yard, its paws kicking up tufts of grass as it spotted a bushy-tailed squirrel darting ahead. With unwavering determination, it chased the nimble creature straight up the rough bark of the old oak tree, leaping and snapping at its heels. Frustrated by the squirrel's escape into the branches above, the dog then unleashed a series of loud, echoing barks that reverberated through the quiet neighborhood.
Judge notes: Excellent expansion with vivid detail and natural flow, but "leaping and snapping at its heels" slightly oversteps the original meaning (the squirrel got away cleanly) and "reverberated through the quiet neighborhood" adds context not implied by the source.

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