# MyCO2 Suite — Emission Factor API (Lookup)

> The factor endpoint returns the underlying emission factor — value, unit, methodology, source, licence, data year, gas basis and GWP version — without performing a calculation. Look up by factor id, activity type, BEA code, or spend classification (MCC / NAICS / ISIC / SIC / NACE) for audit-grade provenance.

Endpoint: GET https://api.myco2suite.io/v1/factor
Price: $0.003 / call (from the first call). Pay with an API key (x-api-key) or, with no signup, via x402 pay-per-call in USDC on Base — a keyless request returns HTTP 402 with machine-readable payment requirements.
Free tier: 1,000 calls/month with a key (get one at https://myco2suite.io).

## Inputs
- id / activity_type / bea_code / mcc (required): One lookup key (also naics / isic / sic / nace)
- country (optional): ISO 3166-1 alpha-2

## Example request
GET https://api.myco2suite.io/v1/factor?mcc=5411&country=US
Header: x-api-key: <your key>   # or pay per call via x402 (no key)

## Example response (JSON)
{
  "factor": {
    "value": 0.2845,
    "unit": "spend-based_kg_co2e_per_usd",
    "methodology": "US EPA USEEIO v2.1",
    "source": "US EPA",
    "licence": "Public Domain"
  }
}

Every response is methodology-stamped: it includes the exact factor value, unit, source, licence, data year, gas basis (CO2 vs CO2e) and GWP version used.

## Common use cases
- Audit and reproduce any emission calculation
- Show data provenance to auditors and regulators
- Browse factors and coverage before integrating

## Related capabilities
- https://myco2suite.io/carbon/transaction (transaction)
- https://myco2suite.io/carbon/activity (activity)

## Links
- Human page: https://myco2suite.io/carbon/factor
- Full API docs: https://myco2suite.io/docs
- Full agent/LLM docs: https://api.myco2suite.io/llms.txt
- Code examples: https://github.com/Jaws22/myco2-examples
- MCP server: https://api.myco2suite.io/v1/mcp (registry: io.myco2suite/carbon-intelligence)
- Contact: admin@myco2suite.io