Concepts & Structured Types

The semantic typing system that gives meaning to your AI data.

Overview

Concepts are Pipelex's type system. They define what kind of data flows through your pipelines — not just the shape, but the meaning. A concept can be as simple as "a tweet about a product" or as complex as "an invoice with line items, totals, and tax breakdowns." Every pipe declares the concepts it accepts as input and produces as output, enabling Pipelex to validate data flow at definition time rather than runtime.

Native Concepts

Pre-built universal concepts available in every Pipelex project:

Dynamic — Dynamic typing, resolved at runtime
Text — Plain text content
Image — Image data (base64, URL, or file path)
Document — A document container (PDF, image, or other file)
Html — HTML content
TextAndImages — Combined text and image content in a single structure
Number — Numeric value
ImgGenPrompt — A prompt specifically crafted for image generation models
Page — A single page extracted from a document, with markdown text and optional images
JSON — Arbitrary JSON data
SearchResult — Web search result with source citations
Anything — Universal type that accepts any content

Custom Concepts

Define your own concepts with natural language descriptions and optional structured fields. Custom concepts live in .mthds files within a domain and can carry a description that guides LLMs, structured fields for validation, or both.

Inline Structures

Define structured fields directly in .mthds files without writing Python. Inline structures support typed fields (text, integer, boolean, number, list) and nested concepts for complex data shapes — making it possible to build fully structured methods without leaving the MTHDS language.

Python StructuredContent Classes

For advanced use cases, generate Pydantic BaseModels from your declarative concepts. This gives you full IDE autocomplete, type checking, and runtime validation. You can also hand-write StructuredContent classes when you need custom logic beyond what MTHDS declarations provide.

Create specialized versions of existing concepts using the refines keyword. Build concept hierarchies for domain modeling — for example, a DetailedInvoice that refines a base Invoice concept, inheriting its structure while adding more specific semantics.

For detailed guidance, see Define Your Concepts.