---
name: json-schema-design-9a34712340f7
description: Design and validate JSON Schemas for API contracts, configuration files, and data exchange formats. Covers schema composition, conditional validation, and code generation from schemas. Triggers on JSON Schema creation, data validation, or API contract design requests.
license: MIT
complexity: intermediate
time_to_learn: 30min
tags:
  - json-schema
  - validation
  - api-contracts
  - data-modeling
governance_phases: [shape, build]
organ_affinity: [meta]
triggers: [user-asks-about-json-schema, context:data-validation, context:api-contract, file-type:*.schema.json]
complements: [api-design-patterns, configuration-management]
---

# JSON Schema Design

Define precise data contracts with JSON Schema for validation, documentation, and code generation.

## Schema Fundamentals

### Basic Types

```json
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://organvm.dev/schemas/repo.json",
  "title": "Repository",
  "description": "An ORGANVM repository entry",
  "type": "object",
  "required": ["name", "organ", "tier", "status"],
  "properties": {
    "name": {
      "type": "string",
      "pattern": "^[a-z][a-z0-9-]*$",
      "minLength": 2,
      "maxLength": 64
    },
    "organ": {
      "type": "string",
      "enum": ["I", "II", "III", "IV", "V", "VI", "VII", "META"]
    },
    "tier": {
      "type": "string",
      "enum": ["flagship", "standard", "infrastructure"]
    },
    "status": {
      "type": "string",
      "enum": ["LOCAL", "CANDIDATE", "PUBLIC_PROCESS", "GRADUATED", "ARCHIVED"]
    },
    "tags": {
      "type": "array",
      "items": { "type": "string" },
      "uniqueItems": true
    }
  },
  "additionalProperties": false
}
```

### Numeric Constraints

```json
{
  "priority": {
    "type": "integer",
    "minimum": 1,
    "maximum": 10
  },
  "score": {
    "type": "number",
    "exclusiveMinimum": 0,
    "maximum": 1.0
  }
}
```

## Composition

### $ref (Reuse)

```json
{
  "$defs": {
    "organ": {
      "type": "string",
      "enum": ["I", "II", "III", "IV", "V", "VI", "VII", "META"]
    },
    "timestamp": {
      "type": "string",
      "format": "date-time"
    }
  },
  "properties": {
    "source_organ": { "$ref": "#/$defs/organ" },
    "target_organ": { "$ref": "#/$defs/organ" },
    "created_at": { "$ref": "#/$defs/timestamp" }
  }
}
```

### allOf (Intersection / Extension)

```json
{
  "allOf": [
    { "$ref": "#/$defs/base-entity" },
    {
      "properties": {
        "extra_field": { "type": "string" }
      }
    }
  ]
}
```

### oneOf (Discriminated Union)

```json
{
  "oneOf": [
    {
      "properties": {
        "type": { "const": "skill" },
        "category": { "type": "string" }
      },
      "required": ["type", "category"]
    },
    {
      "properties": {
        "type": { "const": "bundle" },
        "includes": { "type": "array", "items": { "type": "string" } }
      },
      "required": ["type", "includes"]
    }
  ],
  "discriminator": { "propertyName": "type" }
}
```

### if/then/else (Conditional)

```json
{
  "if": {
    "properties": { "tier": { "const": "flagship" } }
  },
  "then": {
    "required": ["ci_url", "docs_url"]
  }
}
```

## Patterns for Common Needs

### Extensible Enums

```json
{
  "status": {
    "anyOf": [
      { "enum": ["active", "archived", "draft"] },
      { "type": "string", "pattern": "^x-" }
    ]
  }
}
```

### Maps / Dictionaries

```json
{
  "metadata": {
    "type": "object",
    "additionalProperties": { "type": "string" },
    "propertyNames": { "pattern": "^[a-z_]+$" }
  }
}
```

### Nullable Fields

```json
{
  "description": {
    "oneOf": [
      { "type": "string" },
      { "type": "null" }
    ]
  }
}
```

## Validation in Python

```python
import jsonschema
import json
from pathlib import Path

def validate_entry(data: dict, schema_path: str) -> list[str]:
    schema = json.loads(Path(schema_path).read_text())
    validator = jsonschema.Draft202012Validator(schema)
    errors = sorted(validator.iter_errors(data), key=lambda e: list(e.path))
    return [f"{'.'.join(str(p) for p in e.path)}: {e.message}" for e in errors]
```

## Schema Evolution

| Change | Safe? | Strategy |
|--------|-------|----------|
| Add optional field | Yes | No version bump needed |
| Add required field | No | Major version, provide default |
| Remove field | No | Deprecate first, then remove |
| Widen type (string → string\|number) | Yes | Backward compatible |
| Narrow type | No | Major version |
| Add enum value | Yes | Consumers should handle unknown |
| Remove enum value | No | Deprecate first |

## Anti-Patterns

- **No `additionalProperties: false`** — Typos in field names pass silently
- **Overly permissive types** — Use specific types and constraints
- **Inline definitions everywhere** — Extract to `$defs` for reuse
- **No `$id` or `$schema`** — Always specify schema version and identity
- **Validating only on write** — Validate on both read and write boundaries


---
Source attribution: luokai0
Original project: https://github.com/luokai0/ai-agent-skills-by-luo-kai/blob/4d2fb89cdfb75f3f6fd3c6c5ec9ad90ea129eb3c/ai-agent-skills/21-external-registries/18-organvm-skills/development/json-schema-design/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Dave AI resource metadata

Creator / publisher: luokai0
Original project: https://github.com/luokai0/ai-agent-skills-by-luo-kai/blob/4d2fb89cdfb75f3f6fd3c6c5ec9ad90ea129eb3c/ai-agent-skills/21-external-registries/18-organvm-skills/development/json-schema-design/SKILL.md
Attribution basis: Source repository record

Fields of work: Data & Analytics, Development & Engineering, Product Management
Roles: Backend Developer, Data Analyst, ML / AI Engineer, Product Manager, Technical Product Manager
Specialties: API, Backend
Tools: Json Schema
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 1a9e57d07503a288f7dc4fbf98d27191c3d3ed7688c5e624a378d94bbcd21dac