One way teams exploit that - force LLM to go through a predefined task-specific checklist before answering. This custom hard-coded chain of thought boosts the accuracy and makes reasoning more auditable.
I was trying to make a decent cocktail recipe database, and scraped the text of cocktails from about 1400 webpages. Note that this was just the text of the cocktail recipe, and cocktail recipes are comparatively small. I sent the text to an LLM for JSON structuring, and the LLM routinely miscategorized liquor types. It also failed to normalize measurements with explicit instructions and the temperature set to zero. I gave up.
the idea is that instead of using JSON.parse, we create a custom Type.parse for each type you define.
so if you want a:
class Job { company: string[] }
{ "company": "Amazon" }
https://www.boundaryml.com/blog/schema-aligned-parsing
and since its only post processing, the technique will work on every model :)
for example, on BFCL benchmarks, we got SAP + GPT3.5 to beat out GPT4o ( https://www.boundaryml.com/blog/sota-function-calling )
so if you want a:
class Job { company: string[] }
We can upcast "Amazon" -> ["Amazon"] since you indicated that in your schema.
but applicative lifting is a big part of it as well!
gloochat.notion.site/benefits-of-baml
Client: Ollama (phi4) - 90164ms. StopReason: stop. Tokens(in/out): 365/396
---PROMPT---
user: Extract from this content:
Grave Digger:
Ingredients
- 1 1/2 ounces vanilla-infused brandy*
- 3/4 ounce coffee liqueur
- 1/2 ounce Grand Marnier
- 1 ounce espresso, freshly brewed
- Garnish: whipped cream
- Garnish: oreo cookies, crushed
Steps
1. Add all ingredients into a shaker with ice and shake until
well-chilled.
2. Strain into a coupe.
3. Top with whipped cream and crushed Oreo cookies (discarding cream in
center).
*Vanilla-infused brandy: Cut 2 fresh vanilla pods lengthwise and place
into a 750 mL bottle of brandy. Let sit for 3 to 5 days, shaking
occasionally. Strain out pods and store.
IngredientType
----
- Alcohol
- Sweetener
- Sour
- Aromatic
- Bittering_agent
- Food
- Dilution
LiquorType
----
- Gin
- Vodka
- Rum
- Whiskey
- Tequila
- Mezcal
- Brandy
- Cognac
- Liqueur
- Wine
- Absinthe
Answer in JSON using this schema:
{
Name: string,
Ingredients: [
{
Text: string,
Type: IngredientType,
Liquor_type: LiquorType or null,
Name_brand: string or null,
Unit_of_measure: string,
Measurement_or_unit_count: string,
}
],
Steps: [
{
Number: int,
Instruction: string,
}
],
Garnishes: string[],
}
---LLM REPLY---
```json
{
"Name": "Grave Digger",
"Ingredients": [
{
"Text": "vanilla-infused brandy*",
"Type": "Alcohol",
"Liquor_type": "Brandy",
"Name_brand": null,
"Unit_of_measure": "ounces",
"Measurement_or_unit_count": "1 1/2"
},
{
"Text": "coffee liqueur",
"Type": "Liqueur",
"Liquor_type": "Liqueur",
"Name_brand": null,
"Unit_of_measure": "ounce",
"Measurement_or_unit_count": "3/4"
},
{
"Text": "Grand Marnier",
"Type": "Liqueur",
"Liquor_type": "Liqueur",
"Name_brand": "Grand Marnier",
"Unit_of_measure": "ounce",
"Measurement_or_unit_count": "1/2"
},
{
"Text": "espresso, freshly brewed",
"Type": "Bittering_agent",
"Liquor_type": null,
"Name_brand": null,
"Unit_of_measure": "ounces",
"Measurement_or_unit_count": "1"
}
],
"Steps": [
{
"Number": 1,
"Instruction": "Add all ingredients into a shaker with ice and shake until well-chilled."
},
{
"Number": 2,
"Instruction": "Strain into a coupe."
},
{
"Number": 3,
"Instruction": "Top with whipped cream and crushed Oreo cookies (discarding cream in center)."
}
],
"Garnishes": [
"whipped cream",
"oreo cookies, crushed"
]
}
```
---Parsed Response (class Recipe)---
{
"Name": "Grave Digger",
"Ingredients": [
{
"Text": "vanilla-infused brandy*",
"Type": "Alcohol",
"Liquor_type": "Brandy",
"Name_brand": null,
"Unit_of_measure": "ounces",
"Measurement_or_unit_count": "1 1/2"
},
{
"Text": "espresso, freshly brewed",
"Type": "Bittering_agent",
"Liquor_type": null,
"Name_brand": null,
"Unit_of_measure": "ounces",
"Measurement_or_unit_count": "1"
}
],
"Steps": [
{
"Number": 1,
"Instruction": "Add all ingredients into a shaker with ice and shake until well-chilled."
},
{
"Number": 2,
"Instruction": "Strain into a coupe."
},
{
"Number": 3,
"Instruction": "Top with whipped cream and crushed Oreo cookies (discarding cream in center)."
}
],
"Garnishes": [
"whipped cream",
"oreo cookies, crushed"
]
}So, yeah, the main issue being that it dropped some ingredients that were present in the original LLM reply. Separately, the original LLM Reply misclassified the `Type` field in `coffee liqueur`, which should have been `Alcohol`.
the model replied with
{
"Text": "coffee liqueur",
"Type": "Liqueur",
"Liquor_type": "Liqueur",
"Name_brand": null,
"Unit_of_measure": "ounce",
"Measurement_or_unit_count": "3/4"
},
there's no way to cast `Liqueur` -> `IngredientType`. but since the the data model is a `Ingredient[]` we attempted to give you as many ingredients as possible.
The model itself being wrong isn't something we can do much about. that depends on 2 things (the capabilities of the model, and the prompt you pass in).
If you wanted to capture all of the items with more rigor you could write it in this way:
class Recipe {
name string
ingredients Ingredient[]
num_ingredients int
...
// add a constraint on the type
@@assert(counts_match, {{ this.ingredients|length == this.num_ingredients }})
}
{{ ctx.output_format }}
No quotes around strings
To me, it's a criminally underused tool. While "raw" LLMs are cool, they're annoying to use as anything but chatbots, as their output is unpredictable and basically impossible to parse programmatically.
Structured outputs solve that problem neatly. In a way, they're "neural networks without the training". They can be used to solve similar problems as traditional neural networks, things like image classification or extracting information from messy text, but all they require is a Zod or Pydantic type definition and a prompt. No renting GPUs, labeling data and tuning hyperparameters necessary.
They often also improve LLM performance significantly. Imagine you're trying to extract calories per 100g of product, but some product give you calories per serving and a serving size, calories per pound etc. The naive way to do this is a prompt like "give me calories per 100g", but that forces the LLM to do arithmetic, and LLMs are bad at arithmetic. With structured outputs, you just give it the fifteen different formats that you expect to see as alternatives, and use some simple Python to turn them all into calories per 100g on the backend side.