# API Reference: How to Document Your C++

The **API Reference** below is generated from your headers using **Doxygen → Breathe/Exhale**.

To improve the generated pages, add short Doxygen comments in headers, especially for public structs/classes and functions.

## Minimal Examples

### File header
```cpp
/// \file hydro.h
/// Core hydrostatic solver types and interfaces.
```

### Struct/class
```cpp
/// Hydrostatic model container (radius, P, T, rho as functions of mass).
/// Units: P [Pa], T [K], rho [kg m^-3], r [m].
struct HydroModel {
  /// Integrate structure. Throws on EOS lookup failure.
  /// \param m_core Initial mass coordinate [kg]
  /// \param dr Target radial step [m]
  /// \returns Number of steps taken
  int integrate(double m_core, double dr);
};
```

### Function
```cpp
/// Compute adiabatic temperature gradient dT/dP.
/// \param P Pressure [Pa]
/// \param T Temperature [K]
/// \param alpha Thermal expansivity [1/K]
/// \param Cp Heat capacity [J/(kg K)]
/// \param rho Density [kg/m^3]
/// \return dT/dP [K/Pa]
double dT_dP(double P, double T, double alpha, double Cp, double rho);
```

### Grouping related items
```cpp
/// \defgroup eos Equation of State
/// EOS primitives and models.
```

> After adding comments, rebuild docs:
> ```bash
> doxygen Doxyfile && sphinx-build -b html docs docs/_build/html
> ```

The next page, **C++ API Reference**, is auto-generated by Exhale/Breathe from your code.