Structured Output Contracts

Expert

Enforce strict typing and validation constraints on model responses.

01 The Concept

Structured output contracts define the precise data schema (e.g. integer fields, enum lists, and string limits) using schemas like Pydantic or JSON Schema.

Constrained decoders block the generation of tokens that violate this schema, guaranteeing 100% parse success rates for production integrations.

02 Weak vs. Strong

EX 01Pydantic Schema Validation

class ClientDetails(BaseModel): name: str = Field(description='Full legal name') age: int = Field(gt=0, description='Age in years') status: Literal['active', 'inactive'] = Field(description='Current subscription status')

Call API enforcing this schema

→ Why it works

Guarantees data structure. Constrained decoding forces the API to return a shape matching ClientDetails exactly, avoiding malformed tags.

03 Key Points

01JSON Schema: Writing strict definitions of keys, types, and required fields.

02Pydantic Validation: Defining data structures using Python classes for runtime validation.

03Constrained Decoding: Restricting token probabilities at the sampler boundary to match schemas.

04Parser Robustness: Eliminating parsing exceptions and regex scraping workarounds.

05JSON Mode: Instructing the model specifically to output valid stringified JSON formats.

04 Model-Specific Notes

Claude supports structured outputs natively using tool definitions and JSON mode instructions.

05 For Your Role

It's like a customs form: you must write answers inside the boxes provided, and you cannot leave empty columns.

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