schema-prompt

JSON Schema → LLM-ready prompt fragment + output validator. Paste a schema, copy the prompt fragment your LLM consumes for structured output, paste back what came out, see if it conforms.

From the Thoughtworks Technology Radar Vol 34 (Adopt, April 2026): Structured output from LLMs.

Live demo: https://sen.ltd/portfolio/schema-prompt/

特徴

• Schema → prompt fragment: turns properties / types / constraints into natural-language bullets the LLM consumes (the same shape Instructor / Pydantic AI / Outlines produce internally)
• Synthesized example output: shows the JSON shape the LLM should produce — useful as a few-shot anchor in the prompt
• Validator panel: paste the LLM's response, see per-field errors with paths ($.user.age — −5 < minimum 0)
• 5 real-world preset schemas: sentiment + confidence, address parsing, meeting summary, entity extraction, product extraction
• Pure prompt generator + validator (33 unit tests), no LLM API calls, no build step, no dependencies

ローカル起動

npm run serve
# → http://localhost:8080

テスト

npm test

アーキテクチャ

prompt.js    ← Schema → LLM prompt + example generator (15 tests)
validate.js  ← JSON Schema validator subset for LLM output (18 tests)
presets.js   ← 5 real-world schemas + matching sample outputs
app.js       ← UI glue (schema → prompt + example, output → validation)

prompt.js と validate.js は DOM 非依存。document も window も触らない。Node テストでスキーマ生成 + バリデーション両方を完全検証してから UI を組む。

実装している JSON Schema サブセット

LLM workflow が使う構文だけに絞っている:

• type (string / number / integer / boolean / array / object / null + union)
• properties + required
• items + minItems / maxItems
• enum / const
• minimum / maximum
• minLength / maxLength
• pattern (regex)
• format (hint only — no validation)
• description (used by prompt generator)

意図的に対応していないもの: oneOf / anyOf / allOf / $ref / additionalProperties の厳格チェック (LLM 出力では実用上不要)。

ライセンス

MIT. See LICENSE.

Links

• 🌐 Demo: https://sen.ltd/portfolio/schema-prompt/
• 📝 記事: https://qiita.com/sen-ltd/items/410c54015a4722ce1a1a
• 📝 dev.to: https://dev.to/sendotltd/try-the-tech-radar-3-json-schema-llm-prompt-visualised-1ekl