PromptSchema

This is a library to give you BAML style JSON schemas that you can feed to an LLM using your existing dry-schema with annotated types.

Installation

Install the gem and add to the application's Gemfile by executing:

bundle add prompt_schema

If bundler is not being used to manage dependencies, install the gem by executing:

gem install prompt_schema

Usage

Schemas are defined as a class that wraps a regular dry-schema:

schema = Dry::Schema.JSON do
  required(:user).hash do
    required(:email).maybe(:string)
  end
end

prompt_schema = PromptSchema::Schema.new(schema)

For convenience you can use define to have this wrapping be done for you:

schema = PromptSchema.define do
  required(:user).hash do
    required(:email).maybe(:string)
  end
end

schema.is_a?(PromptSchema::Schema) #=> true
schema.dry_schema.is_a?(Dry::Schema) #=> true

result = schema.call({ user: { email: "email@example.com" }})
result.success? #=> true

Using this schema we can print a ready to go prompt.

schema.prompt

Which would return a string of a BAML style prompt:

Answer in JSON using this schema:
{
  user: {
    email: string or null,
  },
}

To get the descriptions we can annotate our own types using dry-types:

module Types
  include Dry.Types()

  Email = Types::String.meta(
    description: "An email address",
    example: "email@example.com"
  )
end

schema = PromptSchema.define do
  required(:user).hash do
    required(:email).maybe(Types::Email)
  end
end

schema.prompt

Which would now annotate the field

Answer in JSON using this schema:
{
  user: {
    // An email address
    // @example email@example.com
    email: string or null,
  },
}

This can be useful to get the best parts of BAML in a ruby native way.

How it works

All Dry::Schema objects have an Abstract Syntax Tree (AST) that we can tap into to build another representation.

We turn the dry schema AST (and its corresponding type schema AST) into a structure that looks like this:

schema = Dry::Schema.Params do
  required(:user).hash do
    required(:email).value(Types::Email)
  end
end

compiled = PromptSchema.compile(schema)

expected = {
  keys: {
    user: {
      type: "hash",
      required: true,
      nullable: false,
      keys: {
        email: {
          type: "string",
          required: true,
          nullable: false,
          example: "email@example.com",
          description: "An email address"
        }
      }
    }
  }
}

compiled == expected #=> true

Then we use a renderer to take this compiled schema and output a string that can be used as part of a prompt.

Rendering of the prompt is handled through a Phlex component. You could take this same representation and write your own version.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/nolantait/prompt_schema.

License

The gem is available as open source under the terms of the MIT License.