# API Specification for Brutto-Netto-Rechner

This document specifies the parameters and usage of our calculation endpoint.

## Calculation Endpoint
`POST /api/mcp/calculate`

Executes the Gross-to-Net or Net-to-Gross salary calculation based on input parameters.

### Request Headers
`Content-Type: application/json`

### Request Body Schema
```json
{
  "grossSalary": number,      // Gross salary in Euros (e.g. 50000)
  "period": "month" | "year", // Default: "year"
  "year": 2024 | 2025 | 2026, // Default: 2026
  "taxClass": 1 | 2 | 3 | 4 | 5 | 6, // Tax class (Steuerklasse). Default: 1
  "hasChildren": boolean,     // Has children? Default: false
  "childCount": number,       // Number of children. Default: 0
  "state": "BW"|"BY"|"BE"|"BB"|"HB"|"HH"|"HE"|"MV"|"NI"|"NW"|"RP"|"SL"|"SN"|"ST"|"SH"|"TH", // German federal state (e.g. "NW" for Nordrhein-Westfalen). Default: "NW"
  "age": number,              // Age in years. Default: 30
  "churchTax": boolean,       // Pays church tax? Default: false
  "healthInsurance": "public" | "private", // Default: "public"
  "healthInsuranceAddOn": number, // Zusatzbeitrag in % (e.g. 1.6). Default: 1.6
  "gwAdvantage": number       // Geldwerter Vorteil (company car etc.) in Euros. Default: 0
}
```

### Response Schema
```json
{
  "gross": number,            // Monthly or annual gross salary
  "net": number,              // Monthly or annual net salary
  "taxes": {
    "incomeTax": number,      // Lohnsteuer
    "soli": number,           // Solidaritätszuschlag (if applicable)
    "churchTax": number       // Kirchensteuer (if applicable)
  },
  "socialSecurity": {
    "healthInsurance": number, // Krankenversicherung (employee share)
    "pensionInsurance": number,// Rentenversicherung (employee share)
    "unemploymentInsurance": number, // Arbeitslosenversicherung (employee share)
    "careInsurance": number   // Pflegeversicherung (employee share)
  },
  "employerCosts": {
    "total": number,          // Total cost to employer
    "healthInsurance": number, // Employer share
    "pensionInsurance": number, // Employer share
    "unemploymentInsurance": number, // Employer share
    "careInsurance": number   // Employer share
  }
}
```

## Supported States (Bundesländer)
- `BW`: Baden-Württemberg
- `BY`: Bayern
- `BE`: Berlin
- `BB`: Brandenburg
- `HB`: Bremen
- `HH`: Hamburg
- `HE`: Hessen
- `MV`: Mecklenburg-Vorpommern
- `NI`: Niedersachsen
- `NW`: Nordrhein-Westfalen
- `RP`: Rheinland-Pfalz
- `SL`: Saarland
- `SN`: Sachsen
- `ST`: Sachsen-Anhalt
- `SH`: Schleswig-Holstein
- `TH`: Thüringen