feat(website): about LlmJson module and related functions.

Author: samchon

.vscode/settings.json

@@ -10,5 +10,4 @@
   "[mdx]": {
     "editor.wordWrap": "on"
   },
-  "typescript.tsdk": "node_modules\\typescript\\lib"
 }

eslint.config.cjs

@@ -0,0 +1,52 @@
+import typia, { ILlmApplication, ILlmFunction, tags } from "typia";
+
+const app: ILlmApplication = typia.llm.application<OrderService>();
+const func: ILlmFunction = app.functions[0];
+
+// Anthropic, Vercel AI, LangChain, MCP already parse JSON internally.
+// However, types are often wrong:
+const fromSdk = {
+  order: {
+    payment: '{"type":"card","cardNumber":"1234-5678"}', // stringified
+    product: {
+      name: "Laptop",
+      price: "1299.99", // string instead of number
+      quantity: "2", // string instead of number
+    },
+    customer: {
+      name: "John Doe",
+      email: "john@example.com",
+      vip: "true", // string instead of boolean
+    },
+  },
+};
+
+const result = func.coerce(fromSdk);
+console.log(result);
+
+interface IOrder {
+  payment: IPayment;
+  product: {
+    name: string;
+    price: number & tags.Minimum<0>;
+    quantity: number & tags.Type<"uint32">;
+  };
+  customer: {
+    name: string;
+    email: string & tags.Format<"email">;
+    vip: boolean;
+  };
+}
+
+type IPayment =
+  | { type: "card"; cardNumber: string }
+  | { type: "bank"; accountNumber: string };
+
+declare class OrderService {
+  /**
+   * Create a new order.
+   *
+   * @param props Order properties
+   */
+  createOrder(props: { order: IOrder }): { id: string };
+}

examples/src/llm/application-coerce.ts

@@ -0,0 +1,55 @@
+import { dedent } from "@typia/utils";
+import typia, { ILlmApplication, ILlmFunction, tags } from "typia";
+
+const app: ILlmApplication = typia.llm.application<OrderService>();
+const func: ILlmFunction = app.functions[0];
+
+// LLM often returns malformed JSON with wrong types
+const llmOutput = dedent`
+  Here is your order:
+
+  \`\`\`json
+  {
+    "order": {
+      "payment": "{\"type\":\"card\",\"cardNumber\":\"1234-5678\"}"
+      "product": {
+        name: "Laptop",
+        price: "1299.99",
+        quantity: 2,
+      },
+      "customer": {
+        "name": "John Doe",
+        "email": "john@example.com",
+        vip: tru
+  \`\`\`
+`;
+
+const result = func.parse(llmOutput);
+if (result.success) console.log(result);
+
+interface IOrder {
+  payment: IPayment;
+  product: {
+    name: string;
+    price: number & tags.Minimum<0>;
+    quantity: number & tags.Type<"uint32">;
+  };
+  customer: {
+    name: string;
+    email: string & tags.Format<"email">;
+    vip: boolean;
+  };
+}
+
+type IPayment =
+  | { type: "card"; cardNumber: string }
+  | { type: "bank"; accountNumber: string };
+
+declare class OrderService {
+  /**
+   * Create a new order.
+   *
+   * @param props Order properties
+   */
+  createOrder(props: { order: IOrder }): { id: string };
+}

examples/src/llm/application-parse.ts

@@ -0,0 +1,56 @@
+import { LlmJson } from "@typia/utils";
+import typia, { ILlmApplication, ILlmFunction, IValidation, tags } from "typia";
+
+const app: ILlmApplication = typia.llm.application<OrderService>();
+const func: ILlmFunction = app.functions[0];
+
+// LLM generated invalid data
+const input = {
+  order: {
+    payment: { type: "card", cardNumber: 12345678 }, // should be string
+    product: {
+      name: "Laptop",
+      price: -100, // violates Minimum<0>
+      quantity: 2.5, // should be uint32
+    },
+    customer: {
+      name: "John Doe",
+      email: "invalid-email", // violates Format<"email">
+      vip: "yes", // should be boolean
+    },
+  },
+};
+
+// Validate and format errors for LLM feedback
+const result: IValidation = func.validate(input);
+if (result.success === false) {
+  const feedback: string = LlmJson.stringify(result);
+  console.log(feedback);
+}
+
+interface IOrder {
+  payment: IPayment;
+  product: {
+    name: string;
+    price: number & tags.Minimum<0>;
+    quantity: number & tags.Type<"uint32">;
+  };
+  customer: {
+    name: string;
+    email: string & tags.Format<"email">;
+    vip: boolean;
+  };
+}
+
+type IPayment =
+  | { type: "card"; cardNumber: string }
+  | { type: "bank"; accountNumber: string };
+
+declare class OrderService {
+  /**
+   * Create a new order.
+   *
+   * @param props Order properties
+   */
+  createOrder(props: { order: IOrder }): { id: string };
+}

examples/src/llm/application-validate.ts

@@ -21,10 +21,10 @@ Automatically installed as a dependency of `typia`.
 | `HttpLlm` | Create LLM controllers from OpenAPI documents and execute function calls |
 | `HttpMigration` | HTTP migration utilities |
 | `HttpError` | HTTP error type |
-| `LlmSchemaConverter` | Convert JSON Schema to LLM schema |
 | `OpenApiConverter` | Convert between OpenAPI versions |
-| `LlmTypeChecker` | Type checker for LLM schemas |
 | `OpenApiTypeChecker` | Type checker for OpenAPI documents |
+| `LlmSchemaConverter` | Convert JSON Schema to LLM schema |
+| `LlmTypeChecker` | Type checker for LLM schemas |
 | `LlmJson` | Parse lenient JSON and format validation errors for LLM-friendly feedback |
 
 ## `LlmJson`

packages/utils/README.md

@@ -4,6 +4,7 @@ export default {
   application: "application() functions",
   parameters: "parameters() function",
   schema: "schema() function",
+  json: "LlmJson module",
   mcp: "Model Context Protocol",
   vercel: "Vercel AI SDK",
   langchain: "LangChain",

website/src/content/docs/llm/_meta.ts

@@ -115,16 +115,69 @@ Structured output is another feature of LLM. The "structured output" means that
 
 > [💻 Playground Link](/playground/?script=JYWwDg9gTgLgBAbzgSQDIBsQEExncAYwEMZgIA7OAXzgDMoIQ4AiAAQGciQCALCgeghgApuSJhgzANwAoUJFhwYATwlE6DJsxVrpMuHPDR4SAEIAjdlliF0wgMrCoAN0LDqGxiwB0-C1ZsCO0cXNz0DAgp2eHEwAC4UDGxcfGJSCjgAXiVVYCJvdExvWNSSMnIAHn9rUiCHJ1cCYQA+AAoASllI8nYIOwKIAHNW2M6gA)
 
+## Lenient JSON Parsing
+
+<LocalSource
+  path="examples/src/llm/application-parse.ts"
+  filename="examples/src/llm/application-parse.ts"
+  showLineNumbers />
+
+Each `ILlmFunction` includes a `parse()` method for handling LLM JSON outputs. This parser is specifically designed for the messy reality of LLM responses:
+
+**Lenient JSON Features:**
+- Unclosed brackets `{`, `[` and strings
+- Trailing commas `[1, 2, 3, ]`
+- JavaScript-style comments (`//` and `/* */`)
+- Unquoted object keys (JavaScript identifier style)
+- Incomplete keywords (`tru`, `fal`, `nul`)
+- Markdown code block extraction (` ```json ... ``` `)
+- Junk text prefix skipping (explanatory text LLMs often add)
+
+**Type Coercion:**
+
+LLMs frequently return wrong types — numbers as strings, booleans as strings, or even double-stringified JSON objects. `func.parse()` automatically coerces these based on the function's parameter schema.
+
+<Callout type="warning">
+**0% → 100% Success Rate on Union Types**
+
+`Qwen3.5` model shows 0% success rate when handling union types with double-stringified JSON objects. With `func.parse()` type coercion, the success rate jumps to 100%.
+</Callout>
+
+<Callout type="info">
+**For Pre-parsed Objects, Use `func.coerce()`**
+
+Some LLM SDKs (Anthropic, Vercel AI, LangChain, MCP) parse JSON internally and return JavaScript objects directly. In these cases, use `func.coerce()` instead of `func.parse()` to fix types without re-parsing.
+
+For more details, see [JSON Utilities](./json).
+</Callout>
+
 ## Validation Feedback
 
-`typia.llm.application<App>()` embeds [`typia.validate<T>()`](/docs/validators/validate) in every function for automatic argument validation. When validation fails, the error is returned as text content with inline `// ❌` comments at each invalid property:
+<LocalSource
+  path="examples/src/llm/application-validate.ts"
+  filename="examples/src/llm/application-validate.ts"
+  showLineNumbers />
+
+`typia.llm.application<App>()` embeds [`typia.validate<T>()`](/docs/validators/validate) in every function for automatic argument validation. When validation fails, use `LlmJson.stringify()` from `@typia/utils` to format errors with inline `// ❌` comments:
 
 ```json
 {
-  "name": "John",
-  "age": "twenty", // ❌ [{"path":"$input.age","expected":"number"}]
-  "email": "not-an-email", // ❌ [{"path":"$input.email","expected":"string & Format<\"email\">"}]
-  "hobbies": "reading" // ❌ [{"path":"$input.hobbies","expected":"Array<string>"}]
+  "order": {
+    "payment": {
+      "type": "card",
+      "cardNumber": 12345678 // ❌ [{"path":"$input.order.payment.cardNumber","expected":"string"}]
+    },
+    "product": {
+      "name": "Laptop",
+      "price": -100, // ❌ [{"path":"$input.order.product.price","expected":"number & Minimum<0>"}]
+      "quantity": 2.5 // ❌ [{"path":"$input.order.product.quantity","expected":"number & Type<\"uint32\">"}]
+    },
+    "customer": {
+      "name": "John Doe",
+      "email": "invalid-email", // ❌ [{"path":"$input.order.customer.email","expected":"string & Format<\"email\">"}]
+      "vip": "yes" // ❌ [{"path":"$input.order.customer.vip","expected":"boolean"}]
+    }
+  }
 }
 ```