Token / Context-Window Cost Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t7-008

Effect

Computation or source lookup only

Input and validation requirements

A zero-valued context window produces an undefined percentage unless explicitly rejected. The specification also does not define the context-token convention or explicitly define an operational branch for requests exceeding the context window, so different implementations can report materially different results.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "model": "gpt-4o",
    "input_tokens": 1000,
    "expected_output_tokens": 500
  },
  "expected_outputs": {
    "total_tokens": 1500,
    "estimated_cost_usd": 0.0125,
    "context_used_percent": 1.171875,
    "context_limit_exceeded": false,
    "input_cost_per_1K_tokens_usd": 0.005,
    "output_cost_per_1K_tokens_usd": 0.015,
    "input_cost_per_1M_tokens_usd": 5,
    "output_cost_per_1M_tokens_usd": 15
  },
  "reference_data": {
    "model": "gpt-4o",
    "context_window_tokens": {
      "value": 128000,
      "source_convention": "OpenAI official model/pricing documentation, as of 2025-02-01, https://openai.com/api/pricing/"
    },
    "input_price_usd_per_1M_tokens": {
      "value": 5,
      "source_convention": "OpenAI official pricing page, as of 2025-02-01, https://openai.com/api/pricing/"
    },
    "output_price_usd_per_1M_tokens": {
      "value": 15,
      "source_convention": "OpenAI official pricing page, as of 2025-02-01, https://openai.com/api/pricing/"
    }
  },
  "working": "Total tokens = 1,000 + 500 = 1,500. Input cost = (1,000 / 1,000,000) × $5.00 = 0.001 × 5.00 = $0.0050. Output cost = (500 / 1,000,000) × $15.00 = 0.0005 × 15.00 = $0.0075. Total cost = $0.0050 + $0.0075 = $0.0125. Context use = (1,500 / 128,000) × 100 = 1.171875%. Per-1K rates: $5.00 / 1,000 = $0.005 input and $15.00 / 1,000 = $0.015 output. The $5.00 and $15.00 per-1M entries are used exactly from the dated table."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json