npx okforest validate .                 # exit 1 on errors; warnings never fail
npx okforest validate . --format json   # for CI and tools
npx okforest inventory .                # types, tags, keys, near-duplicates
npx okforest init sales-okf --template company --name "Sales knowledge"
npx okforest rule okf/type              # why a rule exists, and how to fix it

npx runs it without installing anything. It needs Node.js 22 or later. To run okforest directly, install it globally; in a repository, add it as a development dependency instead, so everyone and CI run the same version:

npm install --global okforest
npm install --save-dev okforest

To also check D2 and Mermaid diagram syntax, install the optional packages alongside it:

npx -p okforest -p @d2lang/d2 -p mermaid okforest validate .
npm install --save-dev okforest @d2lang/d2 mermaid   # or in a repository

In GitHub Actions, use OKForest Validate (uses: okforest/validate-action@v1): the same rules, with annotations on the pull request and the diagram checks included.

Rules, options, and what counts as a concept: see the OKForest CLI README.