npm-package-json-lint is a command-line tool and Node.js library that lints package.json files, ensuring they adhere to best practices and project-specific rules. It helps maintain consistency and quality across projects by enforcing standards for fields like name, version, description, and dependencies. Leveraging a configurable rule set, developers can tailor linting to their specific needs, preventing common errors and improving maintainability. Ideal for CI/CD pipelines.