# Body - Fields { #body-fields }

The same way you can declare additional validation and metadata in *path operation function* parameters with `Query`, `Path` and `Body`, you can declare validation and metadata inside of Pydantic models using Pydantic's `Field`.

## Import `Field` { #import-field }

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning

# Vibe Coding { #vibe-coding }

Are you tired of all that **data validation**, **documentation**, **serialization**, and all that **boring** stuff?

Do you just want to **vibe**? 🎶

**FastAPI** now supports a new `@app.vibe()` decorator that embraces **modern AI coding best practices**. 🤖

## How It Works { #how-it-works }

    /**
     * Constructs and validates a PAC from raw data using provided Kerberos keys.
     * @param data the raw PAC data bytes
     * @param keys map of Kerberos keys for signature validation
     * @throws PACDecodingException if the PAC data is malformed or signature validation fails
     */
    public Pac(byte[] data, Map<Integer, KerberosKey> keys) throws PACDecodingException {
        byte[] checksumData = data.clone();
        try {

        if (errors.isEmpty()) {
            Files.writeString(getReport().toPath(), "Success! No validation errors found.", StandardOpenOption.CREATE);
        } else {
            try (PrintWriter printWriter = new PrintWriter(getReport())) {
                printWriter.printf("Schema: %s%n", jsonSchemaOnDisk);
                printWriter.println("----------Validation Errors-----------");

import org.lastaflute.web.validation.Required;
import org.lastaflute.web.validation.theme.conversion.ValidateTypeFailure;

import jakarta.validation.constraints.Max;
import jakarta.validation.constraints.Min;
import jakarta.validation.constraints.Size;

/**
 * Form class for crawling configuration wizard in the admin interface.
 * Contains validation constraints for creating new crawling configurations.
 */

    }
    return registrySuffixIndexLocal;
  }

  /**
   * Returns an instance of {@link InternetDomainName} after lenient validation. Specifically,
   * validation against <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>
   * ("Internationalizing Domain Names in Applications") is skipped, while validation against <a
   * href="http://www.ietf.org/rfc/rfc1035.txt">RFC 1035</a> is relaxed in the following ways:
   *
   * <ul>

)


def create_model_field(
    name: str,
    type_: Any,
    default: Any | None = Undefined,
    field_info: FieldInfo | None = None,
    alias: str | None = None,
    mode: Literal["validation", "serialization"] = "validation",
) -> ModelField:
    if annotation_is_pydantic_v1(type_):
        raise PydanticV1NotSupportedError(
            "pydantic.v1 models are no longer supported by FastAPI."

  @get:JvmName("noCache") val noCache: Boolean,
  /** If true, this response should not be cached. */
  @get:JvmName("noStore") val noStore: Boolean,
  /** The duration past the response's served date that it can be served without validation. */
  @get:JvmName("maxAgeSeconds") val maxAgeSeconds: Int,
  /**
   * The "s-maxage" directive is the max age for shared caches. Not to be confused with "max-age"

    }

    @Test
    @DisplayName("Should fail validation when not received")
    void testIsValidNotReceived() {
        // When
        boolean valid = response.isValid(mockContext, mockRequest);

        // Then
        assertFalse(valid);
    }

    @Test
    @DisplayName("Should fail validation when signing enforced but not enabled")

import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;
import org.lastaflute.web.ruts.process.ActionRuntime;
import org.lastaflute.web.validation.VaErrorHook;
import org.lastaflute.web.validation.VaMessenger;

import jakarta.annotation.Resource;

/**
 * Admin action for User management.
 *
 */
public class AdminUserAction extends FessAdminAction {

    /**