How are schema tokens estimated?

The tool uses a character-based heuristic of roughly 4 characters per token, which closely tracks how GPT and Claude tokenizers treat compact JSON. It is an estimate, not an exact tokenizer count, but is accurate enough for budgeting.

Why does the schema cost tokens on every request?

With function calling or JSON-schema structured output, the schema is sent as part of the prompt on every single call. A 50-field schema can add hundreds of input tokens per request, which multiplies fast at scale.

Does only input pricing matter here?

The schema lives in the prompt, so it is billed at the input rate. Larger schemas can also pull longer completions, but the dominant, predictable cost is the input overhead, which is what this tool isolates.

Is my schema sent anywhere?

No. Everything runs in your browser. Your schemas are never uploaded, logged or stored.

Structured Extraction Schema Token Cost

Structured extraction schema token cost

When you use function calling or JSON-schema structured output, the schema itself is part of the prompt — it is re-sent on every request. A rich 50-field schema with descriptions can quietly add hundreds of input tokens to each call. Paste two schemas, set your daily volume, and this tool shows the per-request token overhead and the monthly cost difference.

How it works

The tool measures each schema’s character length and estimates tokens at the standard ~4 characters per token ratio that compact JSON tends to follow. It then multiplies the per-request overhead by your daily request count and your model’s input price (per million tokens) to project monthly spend for each schema:

schema_tokens   ≈ schema_characters / 4
monthly_cost    = schema_tokens / 1,000,000 × input_price × requests/day × 30

The difference between the two schemas is the money you save (or spend) purely by changing the shape of what you extract.

Tips and notes

Strip long human-readable description strings from production schemas — they are billed on every call but rarely improve extraction accuracy enough to justify the cost at high volume.
Prefer short, unambiguous field names over verbose ones; dob costs fewer tokens than dateOfBirthInISO8601Format across millions of requests.
If only a few requests need the rich 50-field schema, route those separately and keep the cheap 5-field schema as your default path.