Detecting AI writing tells with an MCP server: Rhythm over vocabulary

jphil-leblanc · reddit · 2026-08-15

The author built an MCP server called Étincel to identify AI-generated prose by analyzing rhythm patterns. The key finding is that AI writing tells are less about vocabulary and more about 'shape': uniform paragraph lengths, low sentence length variance, and forced conclusions. Étincel offers two features: a deterministic audit that scans and reports patterns without rewriting, and a voice layer that learns a user's style to guide models like Claude or Cursor. The author also published accuracy metrics across different registers (e.g., memo 0.909, email 0.540), honestly showcasing the tool's failure in detecting email writing.

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