  We introduce EFTCAMB/EFTCosmoMC as publicly available patches to the commonly
used CAMB/CosmoMC codes. We briefly describe the structure of the codes, their
applicability and main features. To illustrate the use of these patches, we
obtain constraints on parametrized pure EFT and designer $f(R)$ models, both on
$\Lambda$CDM and $w$CDM background expansion histories, using data from Planck
temperature and lensing potential spectra, WMAP low-$\ell$ polarization spectra
(WP), and baryon acoustic oscillation (BAO). Upon inspecting theoretical
stability of the models on the given background, we find non-trivial parameter
spaces that we translate into viability priors. We use different combinations
of data sets to show their individual effects on cosmological and model
parameters. Our data analysis results show that, depending on the adopted data
sets, in the $w$CDM background case this viability priors could dominate the
marginalized posterior distributions. Interestingly, with Planck+WP+BAO+lensing
data, in $f(R)$ gravity models, we get very strong constraints on the constant
dark energy equation of state, $w_0\in(-1,-0.9997)\,\,(95% {\rm C.L.})$.
