https://github.com/nolantait/prompt_schema
Generate BAML style prompts from dry-schema that can get and check structured responses from LLMs
https://github.com/nolantait/prompt_schema
baml dry-schema llm structured-responses
Last synced: 25 days ago
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Generate BAML style prompts from dry-schema that can get and check structured responses from LLMs
- Host: GitHub
- URL: https://github.com/nolantait/prompt_schema
- Owner: nolantait
- License: mit
- Created: 2025-07-06T03:48:44.000Z (3 months ago)
- Default Branch: master
- Last Pushed: 2025-07-31T19:07:14.000Z (2 months ago)
- Last Synced: 2025-09-10T05:24:18.701Z (27 days ago)
- Topics: baml, dry-schema, llm, structured-responses
- Language: Ruby
- Homepage:
- Size: 56.6 KB
- Stars: 7
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE.txt
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README
# PromptSchema
This is a library to give you [BAML](https://github.com/BoundaryML/baml) style
JSON schemas that you can feed to an LLM using your existing
[`dry-schema`](https://github.com/dry-rb/dry-schema) with
annotated types.
## Installation
Install the gem and add to the application's Gemfile by executing:
```bash
bundle add prompt_schema
```
If bundler is not being used to manage dependencies, install the gem by executing:
```bash
gem install prompt_schema
```
## Usage
Schemas are defined as a class that wraps a regular `dry-schema`:
```ruby
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:
```ruby
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
```
Then you can use these schemas to check the data the LLM gives you back just
like you normally do with `dry-schema`.
```ruby
result = schema.call({ user: { email: "email@example.com" }})
result.success? #=> true
result.to_h #=> { user: { email: "email@example.com" }}
```
Using this schema we can print a ready to go prompt.
```ruby
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`:
```ruby
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:
```ruby
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](https://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](https://opensource.org/licenses/MIT).