--- title: RubyLLM::Schema Is Now Schematist: A JSON Schema DSL for... description: RubyLLM::Schema has been extracted and renamed to Schematist, a standalone JSON Schema DSL for Ruby with full Draft 2020-12 coverage. The key breaking change... canonical: https://daily.dev/posts/rubyllm-schema-is-now-schematist-a-json-schema-dsl-for-ruby-with-full-draft-2020-12-coverage-sovn9o2hh twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: RubyLLM::Schema Is Now Schematist: A JSON Schema DSL for Ruby with Full Draft 2020-12 Coverage | daily.dev og:description: RubyLLM::Schema has been extracted and renamed to Schematist, a standalone JSON Schema DSL for Ruby with full Draft 2020-12 coverage. The key breaking change... og:url: https://daily.dev/posts/rubyllm-schema-is-now-schematist-a-json-schema-dsl-for-ruby-with-full-draft-2020-12-coverage-sovn9o2hh og:image: https://api.daily.dev/og/posts/SOvN9O2hH.png og:image:alt: RubyLLM::Schema Is Now Schematist: A JSON Schema DSL for Ruby with Full Draft 2020-12 Coverage og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # RubyLLM::Schema Is Now Schematist: A JSON Schema DSL for Ruby with Full Draft 2020-12 Coverage **[RUBYLAND](https://daily.dev/sources/rubyla)** · 6 min read · 2 upvotes · 0 comments ## Summary RubyLLM::Schema has been extracted and renamed to Schematist, a standalone JSON Schema DSL for Ruby with full Draft 2020-12 coverage. The key breaking change is that `to_json_schema` now returns a proper JSON Schema document (with string keys and `$schema` declared) instead of OpenAI's `response_format` envelope. New features include full composition keywords (`allOf`, `oneOf`, `not`), `unevaluatedProperties`, tuple support via `prefixItems`, `contains` with bounds, encoded content schemas, core keywords like `$dynamicAnchor`/`$dynamicRef`, and proc-based values resolved at render time for dynamic schemas. The gem has zero runtime dependencies. A compatibility shim (`ruby_llm-schema` 1.0.0) aliases old constants with deprecation warnings during migration. RubyLLM 2.0 will depend on Schematist. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I migrate from ruby_llm-schema to schematist in Ruby? Replace the gem 'ruby_llm-schema' dependency with gem 'schematist', rename schema classes from RubyLLM::Schema to Schematist::Schema, and update error handling from RubyLLM::Schema::ValidationError to Schematist::ValidationError. RubyLLM::Helpers becomes Schematist::Helpers. A final ruby_llm-schema 1.0.0 release depends on Schematist and aliases old constants so RubyLLM::Schema keeps resolving, but it warns on load and is the last release under that name. _daily.dev helps developers track gem renames and breaking changes like this before they hit production._ ### Why did to_json_schema in RubyLLM::Schema change its output format? The old to_json_schema returned an OpenAI response_format envelope with keys like name, description, schema, and strict, requiring every non-OpenAI consumer to dig out the actual schema from a nested symbol key. The new Schematist gem's to_json_schema returns the raw Draft 2020-12 JSON Schema document directly, with string keys and a $schema declaration, and drops the OpenAI-specific strict flag entirely since it isn't a JSON Schema keyword. _following breaking API changes like this on daily.dev saves time when upgrading structured-output integrations._ ### What JSON Schema Draft 2020-12 keywords does the Schematist Ruby gem support? Schematist supports the full Draft 2020-12 vocabulary: allOf, oneOf, and not alongside anyOf for composition; unevaluatedProperties for cross-branch validation; propertyNames and patternProperties for object keys; uniqueItems, prefixItems, and contains with bounds for arrays; content_encoding and content_media_type for encoded strings; and core keywords like $id, $anchor, $comment, $dynamicAnchor, $dynamicRef, and $vocabulary passed through as-is. _developers comparing JSON Schema tooling coverage can follow library updates like Schematist's on daily.dev._ ## Similar posts on daily.dev - [JSON schema cache, herb:check, and more\!](https://daily.dev/posts/json-schema-cache-herb-check-and-more--1fdsyvquu) · This Week in Rails · 0 upvotes · 0 comments - [RubyLLM 2.0: Providers, Protocols, and Provider Gems](https://daily.dev/posts/rubyllm-2-0-providers-protocols-and-provider-gems-hvesmpsrq) · RUBYLAND · 2 upvotes · 0 comments - [luismoyano/shiny-json-logic-ruby: A JSONLogic runtime for Ruby that actually works](https://daily.dev/posts/luismoyano-shiny-json-logic-ruby-a-jsonlogic-runtime-for-ruby-that-actually-works-pfuiz5kq3) · Ruby Flow · 0 upvotes · 0 comments - [Why JSON Schema matters more than ever in the age of generative AI](https://daily.dev/posts/why-json-schema-matters-more-than-ever-in-the-age-of-generative-ai-xskn2gm03) · The New Stack · 1 upvotes · 0 comments - [Schema-Enforced JSON Access, Postgres Type Decoding, and more](https://daily.dev/posts/schema-enforced-json-access-postgres-type-decoding-and-more-imamm5zrx) · Rails · 0 upvotes · 0 comments --- Tags: [#ruby](https://daily.dev/tags/ruby), [#rails](https://daily.dev/tags/rails) [View this post on daily.dev](https://daily.dev/posts/rubyllm-schema-is-now-schematist-a-json-schema-dsl-for-ruby-with-full-draft-2020-12-coverage-sovn9o2hh) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"RubyLLM::Schema Is Now Schematist: A JSON Schema DSL for Ruby with Full Draft 2020-12 Coverage","url":"https://daily.dev/posts/rubyllm-schema-is-now-schematist-a-json-schema-dsl-for-ruby-with-full-draft-2020-12-coverage-sovn9o2hh","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/rubyllm-schema-is-now-schematist-a-json-schema-dsl-for-ruby-with-full-draft-2020-12-coverage-sovn9o2hh"},"datePublished":"2026-08-11T12:58:35.207Z","dateModified":"2026-09-13T20:08:36.216Z","description":"RubyLLM::Schema has been extracted and renamed to Schematist, a standalone JSON Schema DSL for Ruby with full Draft 2020-12 coverage. 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