The concise schema-definition vocabulary: the record computation expression, its field and constructor forms, and the collection-schema operations. Optional and opt-in, in the same shape as Reified.DataDSL and Reified.ConstraintDSL: open Reified.Schema for Schema, then open Reified.SchemaDSL for this vocabulary. There is no constraint catalogue here. One Constraint vocabulary serves direct checking, refinement, and Schema, so a field block reaches for Constraint.email or an opened Reified.ConstraintDSL exactly as standalone code does. Boundary supply is Schema-owned and stays here as mustSupply and mayOmit.

Constraint constructors usable without the Constraint. prefix inside a module that declares value rules. Optional vocabulary, not another abstraction. Opening it makes a declaration read minLength 3 instead of Constraint.minLength 3; everything here is the same value the qualified name returns. Some constructors are deliberately left out because they shadow names the same validation code is likely to need in scope: contains, distinct, all, any, length, and between shadow core F# operations. Reach for those as Constraint.contains, Constraint.all, and so on, even inside a module that has opened this DSL. Constraint execution (Constraint.satisfies, Constraint.check, Constraint.guard) is likewise always qualified: ConstraintDSL declares constraints, Constraint.* executes and inspects them. orError and mapError are structural adapters matching the corresponding Result operations. They let a constraint pipeline retain its input and finish with the application's error type without adding an Reified.Result dependency. module SignupRules = open Reified.ConstraintDSL let age : Constraint<int> = atLeast 13 let contact : Constraint<string> = Constraint.all [ present; email ] let requireContact value = value |> Constraint.guard contact |> orError EmailRequired

An abbreviation for the CLI type . Basic Types

An abbreviation for the CLI type . Basic Types

An abbreviation for the CLI type . Basic Types

Record-schema computation expression.

Declares a field, deriving its camel-cased wire name from the property getter. type Signup = { Email: string } field (fun (s: Signup) -> s.Email) // wire name "email"

Declares a field, deriving its camel-cased wire name from the property getter. type Signup = { Email: string } field (fun (s: Signup) -> s.Email) // wire name "email"

Adds portable constraints to the field's inferred schema in declaration order.

Alias for .

Alias for .

Declares a field, deriving its camel-cased wire name from the property getter. type Signup = { Email: string } field (fun (s: Signup) -> s.Email) // wire name "email"

Adds a portable constraint to the field's current schema value.

Alias for .

Declares a field, deriving its camel-cased wire name from the property getter. type Signup = { Email: string } field (fun (s: Signup) -> s.Email) // wire name "email"

Closes a record schema with a total constructor.

Construction, composition, parsing, and checking for universal schemas.

Checks an existing typed value, such as a freely constructed draft, through the schema's constraints, refinements, and record constructor.

Represents an OK or a Successful result. The code succeeded with a value of 'T.

Print to stdout using the given format, and add a newline. The formatter. The formatted result. See Printf.printfn (link: ) for examples.

Represents an Error or a Failure. The code failed with a value of 'TError representing what went wrong.

Functions for inspecting and rendering accumulated schema failures.

Returns failures in deterministic path order.

Functions for building and formatting schema error paths.

Formats a path with dot-separated keys and bracketed indexes.

The location of the failure.

Functions for lowering and rendering boundary schema failures.

Renders a schema error as an English sentence. Constraint violations delegate to Violation.render, so there is one rendering catalogue. SchemaError.render (SchemaError.InvalidFormat "int") // "Expected int format."

The schema failure.

Functions for compiling and running JSON codecs over built model schemas.

Compiles a completed schema into a reusable JSON codec. Compile once per schema, typically at startup, and reuse the codec for every value. Constructor-last object schemas retain a typed record plan, including checked constructors. Constructor failures surface as during decoding. Thrown when is null. Thrown when is incomplete. open Reified.SchemaDSL open Reified.ConstraintDSL type Customer = { Name: string; Email: string } let customerSchema = schema<Customer> { field _.Name { constrain present } field _.Email { constraints [ present; email ] } construct (fun name email -> { Name = name; Email = email }) } let customer = { Name = "Ada"; Email = "ada@example.org" } let codec = Json.compile customerSchema let json = Json.serialize codec customer let roundTripped = Json.deserialize codec json

Serializes a trusted model to a JSON string through a compiled codec. Thrown when is null.

Generates JSON Schema documents from built model schemas. The generator is a pure interpreter over descriptions: it lowers shapes, declared formats, and portable constraint metadata to JSON Schema keywords without parsing input, running checks, or constructing models. One schema declaration therefore drives parsing, validation, and the published contract. Lowering rules: primitives map to type (with format for dates, date-times, and uuids), refined values lower to their underlying primitive representation, nested models to object with properties and required, collections to array with items, maps to object with additionalProperties, and tagged unions to oneOf with a const-constrained discriminator property per case. An option lowers to its payload in an omittable record field, where the codec leaves None out, and to anyOf of its payload and null everywhere the codec writes None as null. Constraint metadata lowers to minLength, maxLength, pattern, enum, minimum/maximum (and exclusive variants), multipleOf, minItems/maxItems, and uniqueItems; constraints without a JSON Schema equivalent, such as trimmed, are skipped. Default-value metadata attached with Schema.withDefault lowers to default.

Generates a compact JSON Schema document from any completed schema declaration. The record, primitive, collection, union, or other completed schema to lower. Thrown when is null. open Reified.SchemaDSL open Reified.ConstraintDSL type Customer = { Name: string; Email: string } let customerSchema = schema<Customer> { field _.Name { constrain present } field _.Email { constraints [ present; email ] } construct (fun name email -> { Name = name; Email = email }) } let document = JsonSchema.generate customerSchema // {"$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{...},"required":[...]}

The inspection API over built schemas and value schemas. Inspect is the entry point for non-validation interpreters: JSON Schema generation, documentation, UI metadata, and codec planning all start from the same descriptions. The returned trees are plain immutable data — inspecting them never parses input, runs checks, or constructs models.

Describes a built model schema as inspectable field metadata. The built model schema to describe. Thrown when is null. Thrown when is not a completed model schema. let description = Inspect.model customerSchema let names = description.Fields |> List.map _.Name