softschema 0.3.0

Soft schema conventions and validation tools for Markdown/YAML artifacts

softschema

Soft schemas: gradual, practical validation for Markdown/YAML artifacts that mix prose and structured data—built for humans and coding agents.

Quick Start

Try it anywhere, with nothing installed but uv or Node. Print the bundled example artifact and its compiled schema, then validate—the artifact is fully self-describing, so no flags are needed:

uvx softschema@latest docs example-artifact > spirited-away.md
uvx softschema@latest docs example-schema > movie-page.schema.yaml
uvx softschema@latest validate spirited-away.md

(Or npx -y softschema@latest ... for the Node implementation; the two are interchangeable.)

To set up softschema in a repository with an agent, tell the agent:

Run uvx softschema@latest --help (for the Python implementation) or npx -y softschema@latest --help (for the Node implementation) and follow the instructions to set up softschema for this repo as a skill.

The help output points the agent to the explicit install command, which writes the portable Agent Skills location and the Claude Code discovery mirror.

What Are Soft Schemas?

Soft schemas are a practice for adding structure gradually to artifacts that mix flexible document context and machine-readable values.

The idea is quite simple, but I’ve found it non-obvious enough that coding agents do not come up with this approach themselves.

However, if given the information and tools in this repo, soft schemas are unreasonably effective. Agents become far better at designing and building complex workflows that mix structured and unstructured data, such as document processing, data extraction, scientific or financial analyses, and many similar applications.

Soft schemas are what we call the general practice. softschema is the name of this repository’s Markdown-and-YAML spec and the matching softschema CLI that implements it.

How Do Soft Schemas Work?

The practice is very simple and language neutral. The simplest approach is to use artifacts in a process or pipeline that are Markdown documents with YAML frontmatter. The YAML carries selected structured values. The Markdown body stays readable for humans and agents and offers additional context. There are no strict rules about duplicating content between Markdown and YAML, but you can gradually adjust and enforce rules.

A hard schema imposes structure up front: define a rigid contract, then reject anything that doesn’t fit. That suits data that is already uniform, but it is a poor fit for documents a human or agent writes, where most of the content is prose and only a few values need to be machine-readable.

A soft schema lets you add structure gradually to the artifacts that pass between steps of a workflow.

Structure runs along a spectrum, and each value moves along it only when it earns the move:

plain Markdown prose
  -> plain Markdown with a few YAML frontmatter values for specific fields
  -> plain Markdown with more YAML fields and a bit of loose validation
  -> plain Markdown with YAML frontmatter fully validated against JSON Schema (or Pydantic/Zod)
  -> plain Markdown with separate structured data files or database records

The structured values live in the YAML payload, the boundary a tool reads, while the prose body stays unconstrained. Validation rules can be easily removed or changed if greater flexibility is needed.

Promote a value into YAML when a tool reads it, validate it at the boundary when correctness matters, and tighten enforcement over time. Each promotion buys efficiency for some downstream consumer, so structure and efficiency grow together, value by value.

Start with processes and data defined in Markdown with data right in the text. Have coding agents try them. Only add structure when it pays for itself.

When and Why Are Soft Schemas Useful?

You should consider using soft schemas if:

1. You wish to have coding agents perform complex processing workflows involving both data and documents

2. Some aspects of the workflow involve structured data that is processed efficiently via code and some aspects are ill-defined

3. The boundary between structured and unstructured data might evolve as you scale and improve the workflows

A plain text document offers flexible context for humans and agents. Structured records are far better when code or agents need to read values consistently and efficiently.

Balancing these needs is often difficult and the source of significant complexity.

Some engineers see the goal of productionizing an agent workflow as the process of converting it to reusable code or structured forms, like relational database schemas.

But the reality is that prematurely structuring data before you understand the structures that best serve a workflow involving code and agents has a cost. At the same time, poorly defined structure has costs in consistency and efficiency.

What is actually needed is gradual addition of structure and flexible addition of textual context at any time.

Soft schemas are simple habits and conventions to make the boundary between structured and unstructured data easier to adjust in either direction as a workflow’s needs for flexibility, consistency, and efficiency evolve (code vs LLM calls). Keeping prose and structured values in one artifact is more convenient and context-efficient. A reader (human or agent) has only one place to look, and information can stay as loose prose until a downstream consumer needs it in more formal schemas.

The Artifact Shape

The default shape is Markdown with YAML frontmatter. The softschema: block is the self-description quartet: contract names the payload contract, schema points at the compiled JSON Schema (relative to the document), envelope names the payload key, and status sets validation strictness:

---
title: Spirited Away (2001)
softschema:
  contract: example.movies:MoviePage/v1
  schema: movie-page.schema.yaml
  envelope: movie
  status: enforced
movie:
  title: Spirited Away
  release_year: 2001
  runtime_minutes: 125
  mpaa_rating: PG
  directors:
    - Hayao Miyazaki
  genres: [Animation, Adventure, Family]
  ratings:
    imdb:
      score: 8.6
      total_votes: 850000
---
# Spirited Away (2001)

*Spirited Away* is Hayao Miyazaki's animated fantasy about ten-year-old Chihiro, who
slips into a spirit world and takes a job in a bathhouse for the gods to free her
parents from the witch Yubaba.
It won the 2003 Academy Award for Best Animated Feature.

The YAML payload is authoritative; a consumer reads it. The Markdown body overlaps with it but is for human readers: the prose adds context like the film’s Academy Award (which no structured field carries), and the full example’s body mirrors some YAML fields as tables for the reader’s convenience.

Only the softschema block and the declared envelope key (movie: above) are softschema’s concern. Additional top-level frontmatter keys, such as the title: above (or description:, tags:, or any other host-specific metadata), are a separate concern: softschema neither forbids nor interprets them, so an artifact can coexist with whatever frontmatter conventions a static-site generator, doc indexer, or other tool already expects. Because the artifact declares envelope: movie, validation still needs no flags.

Every key after contract is optional; a minimal artifact carries contract alone and binds its schema some other way (a --schema flag, or a host registry in library use). Contract IDs follow an enforced shape, [namespace:]Name[/version]—for example example.movies:MoviePage/v1 or com.acme.docs:IncidentReview/1.0—naming a payload contract, not a class or import path.

Validate

A self-describing artifact validates with no flags; flags override the document when you need to point a run elsewhere:

softschema validate doc.md                              # uses the document's bindings
softschema validate doc.md --schema candidate.schema.yaml   # try a different schema
softschema validate doc.md --envelope incident          # designate the payload key

validate reports structural (JSON Schema) and semantic (Pydantic/Zod model) results separately as deterministic JSON. Semantic validation loads a model with --model module:Class (Python) or --model path:export (Zod)—note that --model imports and executes local code, so use it only with trusted models; a compiled schema via --schema executes nothing and is the safe path for untrusted input.

Install

Two supported ways to consume softschema; pick by use:

• Install it as a dependency for projects, CI gates, and library use (reproducible through the project lockfile, fast, offline, and the only way to import it):

  uv add --dev softschema               # Python
  npm install -D softschema@latest      # Node (or: bun add -d)
  

• Zero-install for one-off checks and agent bootstrap:

  uvx softschema@latest --help
  npx -y softschema@latest --help
  

The rule of thumb: if softschema runs more than once, or in CI, or you import it—install it in the project and commit the lockfile. For a quick check or an agent bootstrapping with nothing installed, use a zero-install runner. See Installation for details and the project supply-chain policy.

Use as a Library

Both packages expose the same surface (idiomatic per language). Register contracts at startup and validate at file boundaries:

from pathlib import Path
from softschema import Contract, Contracts, validate_artifact

registry = Contracts()
registry.register(Contract(id="mycorp.docs:IncidentReview/v1", model=IncidentReview,
                           envelope_key="incident"))
result = validate_artifact(Path("incident.md"),
                           contract_id="mycorp.docs:IncidentReview/v1",
                           registry=registry)

import { validateArtifact } from "softschema";

const result = validateArtifact("incident.md", contract);

A host registry’s bindings outrank the document’s own (softschema.schema/envelope), so a document cannot silently redirect a host’s validation; a contract registered without a schema path lets self-describing documents bind themselves. See the softschema Guide for the full playbooks.

Use as an Agent Skill

Both packages ship the same SKILL.md following the open Agent Skills standard. The portable mirror works with agents that discover .agents; the optional Claude mirror supports Claude Code’s discovery path. Pointing an agent at the CLI is enough to bootstrap its understanding of the soft-schema approach: the --help epilog routes it to skill --install, a brief, and the bundled docs.

# Python:
uvx softschema@latest --help            # entry point with skill setup pointers
uvx softschema@latest skill --install --scope project --agent portable --agent claude
uvx softschema@latest skill --brief     # compact operating brief
uvx softschema@latest docs guide        # full mental model and adoption path

# TypeScript (same commands, same bundled docs/skill):
npx -y softschema@latest --help
npx -y softschema@latest skill --install --scope project --agent portable --agent claude
npx -y softschema@latest skill --brief
npx -y softschema@latest docs guide

Self-install the skill into a project so any agent working in the repo finds it natively (either package writes the identical mirrors):

uvx softschema@latest skill --install --scope project --agent portable --agent claude
# or: npx -y softschema@latest skill --install --scope project --agent portable --agent claude
# writes:
#   .agents/skills/softschema/SKILL.md   (Codex, Gemini CLI, cross-agent installers)
#   .claude/skills/softschema/SKILL.md   (Claude Code mirror)

Both mirrors carry a DO NOT EDIT marker. Re-run skill --install to refresh after upgrading the CLI.

Two Synchronized Implementations

softschema ships two complete, fully supported implementations with the same CLI and library surface:

• Python / Pydantic: softschema on PyPI (run as softschema or softschema-py).
• TypeScript / Zod: softschema on npm (run as softschema or softschema-ts).

The two share the same commands, exit classes, structured result meaning, canonical compiled JSON Schema, and schema_sha256 fingerprint. Human-readable presentation and model-native errors may differ where the runtime does; shared vectors and broad CLI journeys keep the portable contract aligned. They release together under the same version number on PyPI and npm.

Further Reading

• softschema Guide: the full mental model and adoption playbooks.
• softschema Spec: the exact artifact format and validation rules.
• Movie Page Example: the complete example backing the snippets above.
• Installation: pinned vs zero-install, uv and Node setup.

Development and Contributing

Repo setup, common commands, CI checks, the parity process, and the release workflow live in Development. The Python and TypeScript implementations must be kept in exact sync: any behavior change goes through the shared golden corpus first and then lands in both packages.