docs: bring README to js-ajv parity

README.md

@@ -1,11 +1,195 @@
 # schemata-validator-php
 
 [![Test](https://github.com/nostrability/schemata-validator-php/actions/workflows/test.yml/badge.svg)](https://github.com/nostrability/schemata-validator-php/actions/workflows/test.yml)
+[![PHP 8.1+](https://img.shields.io/badge/php-8.1+-blue?style=flat-square)](https://php.net)
+[![License](https://img.shields.io/badge/license-GPL--3.0--or--later-blue?style=flat-square)](LICENSE)
 
-PHP validator for [Nostr](https://nostr.com/) JSON schemas. Uses [opis/json-schema](https://opis.io/json-schema/).
+PHP validator for [Nostr](https://nostr.com/) protocol JSON schemas. Built on [`schemata-php`](https://github.com/nostrability/schemata-php) and [opis/json-schema](https://opis.io/json-schema/) (Draft 7).
+
+## Overview
+
+`schemata-validator-php` wraps the `schemata-php` embedded JSON Schema definitions with Opis validation, exposing ready-to-use static methods for common Nostr data structures. It validates Nostr events by kind and NIP-11 relay information documents.
+
+Validation results separate hard errors (schema violations) from soft warnings (missing schemas for unknown kinds).
 
 ## When to use this
-JSON Schema validation is [not suited for runtime hot paths](https://github.com/nostrability/schemata#what-is-it-not-good-for). Use in **CI and integration tests**.
+
+JSON Schema validation is [not suited for runtime hot paths](https://github.com/nostrability/schemata#what-is-it-not-good-for). Use this in:
+
+- **CI pipelines** catching schema drift during builds
+- **Integration tests** for clients and relays
+- **PHPUnit suites** verifying event construction correctness
+
+## Installation
+
+Add to your `composer.json`:
+
+```json
+{
+    "require-dev": {
+        "nostrability/schemata-validator": "dev-main"
+    },
+    "repositories": [
+        { "type": "vcs", "url": "https://github.com/nostrability/schemata-validator-php" }
+    ]
+}
+```
+
+Then run:
+
+```bash
+composer install
+```
+
+The `schemata-php` data package is also required. Clone it as a sibling directory:
+
+```bash
+git clone https://github.com/nostrability/schemata-php.git ../schemata-php
+```
+
+Requires PHP `>=8.1` and `opis/json-schema ^2.0`.
+
+## Quick Start
+
+```php
+use Nostrability\SchemataValidator\SchemataValidator;
+
+$event = [
+    'id' => str_repeat('a', 64),
+    'pubkey' => str_repeat('b', 64),
+    'created_at' => 1700000000,
+    'kind' => 1,
+    'tags' => [],
+    'content' => 'hello world',
+    'sig' => str_repeat('c', 128),
+];
+
+$result = SchemataValidator::validateNote($event);
+assert($result->valid, 'Errors: ' . print_r($result->errors, true));
+// $result->errors is empty, $result->warnings may flag unknown kinds
+```
+
+## API
+
+All methods are static on `SchemataValidator`.
+
+### `SchemataValidator::validate($schema, $data)`
+
+```php
+public static function validate(array $schema, mixed $data): ValidationResult
+```
+
+Low-level validator. Compiles a JSON Schema with Opis and validates `$data` against it. Strips nested `$id`/`$schema` fields from the schema to prevent resolution issues. Use `validateNote` or `validateNip11` for common cases.
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `$schema` | `array` | A JSON Schema document as a PHP array |
+| `$data` | `mixed` | The data to validate |
+
+### `SchemataValidator::validateNote($event)`
+
+```php
+public static function validateNote(array $event): ValidationResult
+```
+
+Validates a Nostr event against the schema for its `kind`. The schema is looked up from `schemata-php` using the key `kind{N}Schema`. Returns a warning (not an error) if no schema exists for the given kind.
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `$event` | `array` | A Nostr event as an associative array |
+
+### `SchemataValidator::validateNip11($doc)`
+
+```php
+public static function validateNip11(array $doc): ValidationResult
+```
+
+Validates a NIP-11 relay information document — the metadata object a relay serves at its HTTP endpoint — against the `nip11Schema`.
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `$doc` | `array` | A NIP-11 relay info document as an associative array |
+
+### `SchemataValidator::getSchema($key)`
+
+```php
+public static function getSchema(string $key): ?array
+```
+
+Looks up a schema by key from the `schemata-php` registry. Returns `null` if the key doesn't exist.
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `$key` | `string` | Schema registry key (e.g., `"kind1Schema"`, `"pTagSchema"`) |
+
+### `ValidationResult`
+
+```php
+class ValidationResult {
+    public bool $valid;
+    public array $errors;   // ValidationError[]
+    public array $warnings; // ValidationError[]
+}
+```
+
+- `$valid` — `true` if the data passes all schema constraints
+- `$errors` — schema violations; empty when `$valid` is `true`
+- `$warnings` — unknown kind / missing schema alerts
+
+### `ValidationError`
+
+```php
+class ValidationError {
+    public string $instancePath;
+    public string $keyword;
+    public string $message;
+    public string $schemaPath;
+}
+```
+
+## Usage Examples
+
+**Event validation:**
+
+```php
+$result = SchemataValidator::validateNote([
+    'id' => str_repeat('a', 64), 'pubkey' => str_repeat('b', 64),
+    'created_at' => 1700000000, 'kind' => 1, 'tags' => [],
+    'content' => 'hello world', 'sig' => str_repeat('c', 128),
+]);
+assert($result->valid);
+```
+
+**NIP-11 validation:**
+
+```php
+$result = SchemataValidator::validateNip11([
+    'name' => 'My Relay',
+    'supported_nips' => [1, 11],
+]);
+assert($result->valid);
+```
+
+**Direct schema lookup:**
+
+```php
+$schema = SchemataValidator::getSchema('kind1Schema');
+assert($schema !== null);
+```
+
+## Known Limitations
+
+- **Partial kind coverage:** Only event kinds with a corresponding schema in `@nostrability/schemata` can be validated. `validateNote` returns a warning (not an error) when no schema exists for the given kind.
+- **No `validateMessage`:** Protocol message validation is not yet implemented in this package.
+- **No recursive content validation:** The `content` field of events containing stringified JSON (e.g., kind 0 metadata) is not recursively validated.
+- **Alpha accuracy:** False positives and negatives are possible. The underlying schemas are in active development.
+
+## Related Packages
+
+- [`schemata-php`](https://github.com/nostrability/schemata-php) — PHP data package containing embedded schemas and registry
+- [`@nostrability/schemata`](https://github.com/nostrability/schemata) — canonical language-agnostic schema definitions
+- [`@nostrwatch/schemata-js-ajv`](https://github.com/sandwichfarm/nostr-watch/tree/next/libraries/schemata-js-ajv) — JavaScript/TypeScript validator implementation
 
 ## License
-GPL-3.0-or-later
+
+[GPL-3.0-or-later](LICENSE)