RDoc vs Scalar

RDoc is free software for producing Ruby project documentation as HTML pages and command-line reference output. The `rdoc` command generates documentation, while `ri` displays it. It processes Ruby, C, and RBS source files, plus RDoc markup, Markdown, RD, and TomDoc documents. RBS declarations can describe classes, modules, methods, attributes, and constants, and can add comments or type signatures to matching Ruby source documentation. A local preview server watches source files and refreshes the browser after changes. It uses Ruby’s built-in TCPServer and needs no external gems, but provides neither HTTPS nor HTTP/2 and is intended only for local previews. RDoc reports documentation coverage with `rdoc -C`, or includes parameter names with `rdoc -C1`. Generation can be automated through Rake or the RDoc API. Aliki is the default theme; Darkfish is deprecated. Ruby 3.2.0 or newer is required for the current gem.

Scalar is a set of API products for documentation, SDK generation, API registries, API requests, and MCP server use. Scalar Docs combines product guides and interactive API references generated from OpenAPI documents in a developer portal. Teams can write in Markdown or MDX, use GitHub content, preview pull requests, and publish through a CLI or after a merge. The SDK Generator builds idiomatic, type-safe client libraries from OpenAPI documents and can publish them through repository pull requests. Registry stores and versions OpenAPI and AsyncAPI documents, JSON Schema, and Spectral rules with Git integration. The open-source API Client works offline for sending requests, organizing collections, and testing APIs from OpenAPI documents. Scalar supports hosted and self-hosted deployment. Its Free plan is free and includes up to three APIs, one SDK with up to 25 endpoints, one editor seat, and 50 Agent Scalar credits. Pro is $150 a month; Business is $600 a month. Scalar states that it has received a SOC 2 Type 1 report and maintains GDPR-compliant privacy practices.