JSON schema for AT Protocol lexicon documents

schema.json

{
  "type": "object",
  "properties": {
    "lexicon": { "type": "number", "const": 1 },
    "id": {
      "type": "string",
      "pattern": "^[a-zA-Z]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(\\.[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+(\\.[a-zA-Z]([a-zA-Z]{0,61}[a-zA-Z])?)$"
    },
    "revision": { "type": "integer", "minimum": 0 },
    "description": { "type": "string" },
    "defs": {
      "anyOf": [
        {
          "type": "object",
          "properties": {
            "main": { "$ref": "#/definitions/RecordSchema" },
            "record": { "not": {} }
          },
          "required": ["main"],
          "additionalProperties": { "$ref": "#/definitions/UserTypeSchema" }
        },
        {
          "type": "object",
          "properties": {
            "main": {
              "anyOf": [
                { "$ref": "#/definitions/XrpcQuerySchema" },
                { "$ref": "#/definitions/XrpcProcedureSchema" }
              ]
            },
            "params": { "not": {} },
            "input": { "not": {} },
            "output": { "not": {} },
            "errors": { "not": {} }
          },
          "required": ["main"],
          "additionalProperties": { "$ref": "#/definitions/UserTypeSchema" }
        },
        {
          "type": "object",
          "properties": {
            "main": { "$ref": "#/definitions/XrpcSubscriptionSchema" },
            "params": { "not": {} },
            "message": { "not": {} }
          },
          "required": ["main"],
          "additionalProperties": { "$ref": "#/definitions/UserTypeSchema" }
        },
        {
          "type": "object",
          "additionalProperties": { "$ref": "#/definitions/UserTypeSchema" }
        }
      ]
    },
    "$schema": { "type": "string" }
  },
  "required": ["lexicon", "id", "defs"],
  "additionalProperties": false,
  "definitions": {
    "ArraySchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "array" },
        "description": { "type": "string" },
        "items": {
          "anyOf": [
            { "$ref": "#/definitions/PrimitiveSchema" },
            { "$ref": "#/definitions/IpldTypeSchema" },
            { "$ref": "#/definitions/BlobSchema" },
            { "$ref": "#/definitions/RefVariantSchema" }
          ]
        },
        "maxLength": { "type": "integer", "minimum": 0 },
        "minLength": { "type": "integer", "minimum": 0 }
      },
      "required": ["type", "items"],
      "additionalProperties": false
    },
    "BaseStringSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "string" },
        "description": { "type": "string" },
        "default": { "type": "string" },
        "const": { "type": "string" },
        "enum": { "type": "array", "items": { "type": "string" } },
        "knownValues": { "type": "array", "items": { "type": "string" } }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "BlobSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "blob" },
        "description": { "type": "string" },
        "accept": { "type": "array", "items": { "type": "string" } },
        "maxSize": { "type": "integer", "minimum": 0 }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "BooleanSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "boolean" },
        "description": { "type": "string" },
        "default": { "type": "boolean" },
        "const": { "type": "boolean" }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "BytesSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "bytes" },
        "description": { "type": "string" },
        "maxLength": { "type": "integer", "minimum": 0 },
        "minLength": { "type": "integer", "minimum": 0 }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "CidLinkSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "cid-link" },
        "description": { "type": "string" }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "FormattedStringSchema": {
      "type": "object",
      "properties": {
        "type": { "$ref": "#/definitions/BaseStringSchema/properties/type" },
        "description": {
          "$ref": "#/definitions/BaseStringSchema/properties/description"
        },
        "default": {
          "$ref": "#/definitions/BaseStringSchema/properties/default"
        },
        "const": { "$ref": "#/definitions/BaseStringSchema/properties/const" },
        "enum": { "$ref": "#/definitions/BaseStringSchema/properties/enum" },
        "knownValues": {
          "$ref": "#/definitions/BaseStringSchema/properties/knownValues"
        },
        "format": {
          "type": "string",
          "enum": [
            "at-identifier",
            "at-uri",
            "cid",
            "datetime",
            "did",
            "handle",
            "language",
            "nsid",
            "record-key",
            "tid",
            "uri"
          ]
        }
      },
      "required": ["type", "format"],
      "additionalProperties": false
    },
    "IntegerSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "integer" },
        "description": { "type": "string" },
        "default": { "type": "integer", "minimum": 0 },
        "const": { "type": "integer", "minimum": 0 },
        "enum": {
          "type": "array",
          "items": { "type": "integer", "minimum": 0 }
        },
        "maximum": { "type": "integer", "minimum": 0 },
        "minimum": { "type": "integer", "minimum": 0 }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "IpldTypeSchema": {
      "anyOf": [
        { "$ref": "#/definitions/BytesSchema" },
        { "$ref": "#/definitions/CidLinkSchema" }
      ]
    },
    "MainUserTypeSchema": {
      "anyOf": [
        { "$ref": "#/definitions/RecordSchema" },
        { "$ref": "#/definitions/XrpcQuerySchema" },
        { "$ref": "#/definitions/XrpcProcedureSchema" },
        { "$ref": "#/definitions/XrpcSubscriptionSchema" },
        { "$ref": "#/definitions/BlobSchema" },
        { "$ref": "#/definitions/ArraySchema" },
        { "$ref": "#/definitions/TokenSchema" },
        { "$ref": "#/definitions/ObjectSchema" },
        { "$ref": "#/definitions/BooleanSchema" },
        { "$ref": "#/definitions/IntegerSchema" },
        { "$ref": "#/definitions/StringSchema" },
        { "$ref": "#/definitions/BytesSchema" },
        { "$ref": "#/definitions/CidLinkSchema" },
        { "$ref": "#/definitions/UnknownSchema" }
      ]
    },
    "ObjectSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "object" },
        "description": { "type": "string" },
        "required": {
          "type": "array",
          "items": { "type": "string" },
          "default": []
        },
        "nullable": {
          "type": "array",
          "items": { "type": "string" },
          "default": []
        },
        "properties": {
          "type": "object",
          "additionalProperties": {
            "anyOf": [
              { "$ref": "#/definitions/RefVariantSchema" },
              { "$ref": "#/definitions/IpldTypeSchema" },
              { "$ref": "#/definitions/ArraySchema" },
              { "$ref": "#/definitions/BlobSchema" },
              { "$ref": "#/definitions/PrimitiveSchema" }
            ]
          }
        }
      },
      "required": ["type", "properties"],
      "additionalProperties": false
    },
    "PrimitiveArraySchema": {
      "type": "object",
      "properties": {
        "type": { "$ref": "#/definitions/ArraySchema/properties/type" },
        "description": {
          "$ref": "#/definitions/ArraySchema/properties/description"
        },
        "items": { "$ref": "#/definitions/PrimitiveSchema" },
        "maxLength": {
          "$ref": "#/definitions/ArraySchema/properties/maxLength"
        },
        "minLength": {
          "$ref": "#/definitions/ArraySchema/properties/minLength"
        }
      },
      "required": ["type", "items"],
      "additionalProperties": false
    },
    "PrimitiveSchema": {
      "anyOf": [
        { "$ref": "#/definitions/BooleanSchema" },
        { "$ref": "#/definitions/IntegerSchema" },
        { "$ref": "#/definitions/StringSchema" },
        { "$ref": "#/definitions/UnknownSchema" }
      ]
    },
    "RecordSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "record" },
        "description": { "type": "string" },
        "key": { "type": "string" },
        "record": { "$ref": "#/definitions/ObjectSchema" }
      },
      "required": ["type", "record"],
      "additionalProperties": false
    },
    "RefSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "ref" },
        "description": { "type": "string" },
        "ref": {
          "type": "string",
          "minLength": 1,
          "pattern": "^(?=.)(?:[a-zA-Z](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+(?:\\.[a-zA-Z](?:[a-zA-Z]{0,61}[a-zA-Z])?))?(?:#[a-zA-Z](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)?$"
        }
      },
      "required": ["type", "ref"],
      "additionalProperties": false
    },
    "RefUnionSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "union" },
        "description": { "type": "string" },
        "refs": {
          "type": "array",
          "items": { "$ref": "#/definitions/RefSchema/properties/ref" }
        },
        "closed": { "type": "boolean", "default": false }
      },
      "required": ["type", "refs"],
      "additionalProperties": false
    },
    "RefVariantSchema": {
      "anyOf": [
        { "$ref": "#/definitions/RefSchema" },
        { "$ref": "#/definitions/RefUnionSchema" }
      ]
    },
    "StringSchema": {
      "anyOf": [
        { "$ref": "#/definitions/UnformattedStringSchema" },
        { "$ref": "#/definitions/FormattedStringSchema" }
      ]
    },
    "TokenSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "token" },
        "description": { "type": "string" }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "UnformattedStringSchema": {
      "type": "object",
      "properties": {
        "type": { "$ref": "#/definitions/BaseStringSchema/properties/type" },
        "description": {
          "$ref": "#/definitions/BaseStringSchema/properties/description"
        },
        "default": {
          "$ref": "#/definitions/BaseStringSchema/properties/default"
        },
        "const": { "$ref": "#/definitions/BaseStringSchema/properties/const" },
        "enum": { "$ref": "#/definitions/BaseStringSchema/properties/enum" },
        "knownValues": {
          "$ref": "#/definitions/BaseStringSchema/properties/knownValues"
        },
        "format": { "not": {} },
        "maxLength": { "type": "integer", "exclusiveMinimum": 0 },
        "minLength": { "type": "integer", "exclusiveMinimum": 0 },
        "maxGraphemes": { "type": "integer", "exclusiveMinimum": 0 },
        "minGraphemes": { "type": "integer", "exclusiveMinimum": 0 }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "UnknownSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "unknown" },
        "description": { "type": "string" }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "UserTypeSchema": {
      "anyOf": [
        { "$ref": "#/definitions/BlobSchema" },
        { "$ref": "#/definitions/ArraySchema" },
        { "$ref": "#/definitions/TokenSchema" },
        { "$ref": "#/definitions/ObjectSchema" },
        { "$ref": "#/definitions/BooleanSchema" },
        { "$ref": "#/definitions/IntegerSchema" },
        { "$ref": "#/definitions/StringSchema" },
        { "$ref": "#/definitions/BytesSchema" },
        { "$ref": "#/definitions/CidLinkSchema" },
        { "$ref": "#/definitions/UnknownSchema" }
      ]
    },
    "XrpcBodySchema": {
      "type": "object",
      "properties": {
        "description": { "type": "string" },
        "encoding": { "type": "string" },
        "schema": {
          "anyOf": [
            { "$ref": "#/definitions/RefVariantSchema" },
            { "$ref": "#/definitions/ObjectSchema" }
          ]
        }
      },
      "required": ["encoding"],
      "additionalProperties": false
    },
    "XrpcErrorSchema": {
      "type": "object",
      "properties": {
        "name": { "type": "string" },
        "description": { "type": "string" }
      },
      "required": ["name"],
      "additionalProperties": false
    },
    "XrpcParametersSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "params" },
        "description": { "type": "string" },
        "required": {
          "type": "array",
          "items": { "type": "string" },
          "default": []
        },
        "properties": {
          "type": "object",
          "additionalProperties": {
            "anyOf": [
              { "$ref": "#/definitions/PrimitiveSchema" },
              { "$ref": "#/definitions/PrimitiveArraySchema" }
            ]
          }
        }
      },
      "required": ["type", "properties"],
      "additionalProperties": false
    },
    "XrpcProcedureSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "procedure" },
        "description": { "type": "string" },
        "parameters": { "$ref": "#/definitions/XrpcParametersSchema" },
        "input": { "$ref": "#/definitions/XrpcBodySchema" },
        "output": { "$ref": "#/definitions/XrpcBodySchema" },
        "errors": {
          "type": "array",
          "items": { "$ref": "#/definitions/XrpcErrorSchema" }
        }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "XrpcQuerySchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "query" },
        "description": { "type": "string" },
        "parameters": { "$ref": "#/definitions/XrpcParametersSchema" },
        "output": { "$ref": "#/definitions/XrpcBodySchema" },
        "errors": {
          "type": "array",
          "items": { "$ref": "#/definitions/XrpcErrorSchema" }
        }
      },
      "required": ["type"],
      "additionalProperties": false
    },
    "XrpcSubscriptionMessageSchema": {
      "type": "object",
      "properties": {
        "description": { "type": "string" },
        "schema": {
          "anyOf": [
            { "$ref": "#/definitions/RefVariantSchema" },
            { "$ref": "#/definitions/ObjectSchema" }
          ]
        }
      },
      "additionalProperties": false
    },
    "XrpcSubscriptionSchema": {
      "type": "object",
      "properties": {
        "type": { "type": "string", "const": "subscription" },
        "description": { "type": "string" },
        "parameters": { "$ref": "#/definitions/XrpcParametersSchema" },
        "message": { "$ref": "#/definitions/XrpcSubscriptionMessageSchema" },
        "errors": {
          "type": "array",
          "items": { "$ref": "#/definitions/XrpcErrorSchema" }
        }
      },
      "required": ["type"],
      "additionalProperties": false
    }
  },
  "$schema": "http://json-schema.org/draft-07/schema#"
}

.definitions.RefSchema.properties.ref.pattern doesn't properly match against local refs or references to named types via fragments (i..e, #localdef, com.atproto.server.defs#someDef). ATProto specs mentions the following:

A fragment may be appended to an NSID in some contexts to refer to a specific sub-field within the schema. The fragment is separated from the NSID by an ASCII hash character (#). The fragment identifier string (after the #) has the same syntax restrictions as the final segment of an NSID: ASCII alphabetic, one or more characters, length restricted, etc.

Thus, this can be fixed by changing the pattern to the following:

^(?:(?:[a-zA-Z](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)+(?:\\.[a-zA-Z](?:[a-zA-Z]{0,61}[a-zA-Z])?)(?:#[a-zA-Z](?:[a-zA-Z]{0,61}[a-zA-Z])?)?)|(?:#[a-zA-Z](?:[a-zA-Z]{0,61}[a-zA-Z])?))$

This is fixed now, I might move them elsewhere like https://boat.kelinci.net/lexicon-schema.json, but I have no plans for this yet.