Hi Nicolas,

I've tackled it and made it work with some sort of simplification,
please see v3 following this email.

CLI tools are merged into one package:
--8<---------------cut here---------------start------------->8---
> tree $(./pre-inst-env guix build age)
/gnu/store/wpaqwb40l2bzzbgjyqkn177mwc7f0v3l-age-1.2.1
├── bin
│   ├── age
│   └── age-keygen
├── etc
│   └── ld.so.cache
└── share
    ├── doc
    │   └── age-1.2.1
    │       └── LICENSE
    └── man
        └── man1
            ├── age.1.zst
            └── age-keygen.1.zst

8 directories, 6 files
--8<---------------cut here---------------end--------------->8---

And versions:
--8<---------------cut here---------------start------------->8---
> $(./pre-inst-env guix build age)/bin/age --version
1.2.1
[env: /gnu/store/gpahyx6mjm17ydpxyxvry2pqiwm7kdj5-profile]
> $(./pre-inst-env guix build age)/bin/age-keygen --version
1.2.1
[env: /gnu/store/gpahyx6mjm17ydpxyxvry2pqiwm7kdj5-profile]
--8<---------------cut here---------------end--------------->8---

Please check if it works with Emacs' package now.

---
Oleg