technical-term · Harness & runtime · maturing · Reviewed

Structured output

Model output constrained to a declared machine-readable schema so software can parse and validate its shape.

Definition

Structured output makes a probabilistic model produce data against a defined schema, improving interoperability and reducing parsing ambiguity. Schema validity establishes shape—not factual correctness, business validity, authorization, or safe effect.

Schema-constrained generation is widely supported, though guarantees and failure handling differ across model APIs.

Why it matters

Typed boundaries make model decisions easier to inspect, test, reject, and route.

Semantic validation and policy evaluation must still occur in trusted code.

System anatomy

Schema
Allowed fields, types, enumerations, and required values.
Validation
Trusted checks for structure and domain constraints.
Disposition
Accept, repair, reject, or escalate invalid output.

Important distinctions

Correct output
A response can satisfy the schema while containing false or unsafe values.
Tool authorization
Typed arguments make validation possible but do not grant permission to execute.

Implementation signals

  • Keep schemas narrow and versioned
  • Validate domain invariants after parsing
  • Fail closed for consequential actions

Failure modes

  • Automatic repair changes meaning without review
  • Free-form strings smuggle unvalidated instructions into typed fields

Sources and further study

  1. OpenAI — A practical guide to building agents

    Defines a practical agent around a model, tools, instructions, and a run loop that continues until an exit condition is reached.

    Use in this library: Primary definition. The guide is first-party product guidance and a simplified starting architecture, not a complete regulated-enterprise control model.

    guidance · guidance · Published 2025
  2. Model Context Protocol — Model Context Protocol architecture overview

    Documents the host, client, server, capability-negotiation, and message layers used to connect AI applications with context and tools.

    Use in this library: Standard or protocol. Protocol connectivity and capability discovery do not confer business authority, validate tool output, or make a server trustworthy.

    protocol · protocol · Published 2026-07-28