diff --git a/python/valuecell/server/api/exceptions.py b/python/valuecell/server/api/exceptions.py
new file mode 100644
index 000000000..1f0d9d3e3
--- /dev/null
+++ b/python/valuecell/server/api/exceptions.py
@@ -0,0 +1,107 @@
+"""API exception handling module."""
+
+from typing import Dict, Any
+from fastapi import HTTPException, Request
+from fastapi.responses import JSONResponse
+from fastapi.exceptions import RequestValidationError
+
+from .schemas import ErrorResponse, StatusCode
+
+
+class APIException(Exception):
+    """Custom API exception base class."""
+
+    def __init__(self, code: StatusCode, message: str, details: Dict[str, Any] = None):
+        self.code = code
+        self.message = message
+        self.details = details or {}
+        super().__init__(message)
+
+
+class UnauthorizedException(APIException):
+    """Unauthorized exception."""
+
+    def __init__(self, message: str = "Unauthorized access"):
+        super().__init__(StatusCode.UNAUTHORIZED, message)
+
+
+class NotFoundException(APIException):
+    """Resource not found exception."""
+
+    def __init__(self, message: str = "Resource not found"):
+        super().__init__(StatusCode.NOT_FOUND, message)
+
+
+class ForbiddenException(APIException):
+    """Forbidden access exception."""
+
+    def __init__(self, message: str = "Forbidden access"):
+        super().__init__(StatusCode.FORBIDDEN, message)
+
+
+class InternalServerException(APIException):
+    """Internal server error exception."""
+
+    def __init__(self, message: str = "Internal server error"):
+        super().__init__(StatusCode.INTERNAL_ERROR, message)
+
+
+async def api_exception_handler(request: Request, exc: APIException) -> JSONResponse:
+    """API exception handler."""
+    return JSONResponse(
+        status_code=200,  # HTTP status code is always 200, error info is in response body
+        content=ErrorResponse.create(code=exc.code, msg=exc.message).dict(),
+    )
+
+
+async def http_exception_handler(request: Request, exc: HTTPException) -> JSONResponse:
+    """HTTP exception handler."""
+    # Map HTTP status codes to our status codes
+    status_code_mapping = {
+        400: StatusCode.BAD_REQUEST,
+        401: StatusCode.UNAUTHORIZED,
+        403: StatusCode.FORBIDDEN,
+        404: StatusCode.NOT_FOUND,
+        500: StatusCode.INTERNAL_ERROR,
+    }
+
+    api_code = status_code_mapping.get(exc.status_code, StatusCode.INTERNAL_ERROR)
+    return JSONResponse(
+        status_code=200,
+        content=ErrorResponse.create(code=api_code, msg=str(exc.detail)).dict(),
+    )
+
+
+async def validation_exception_handler(
+    request: Request, exc: RequestValidationError
+) -> JSONResponse:
+    """Request validation exception handler."""
+    # Extract validation error information
+    error_details = []
+    for error in exc.errors():
+        error_details.append(
+            {
+                "field": ".".join(str(x) for x in error["loc"]),
+                "message": error["msg"],
+                "type": error["type"],
+            }
+        )
+
+    return JSONResponse(
+        status_code=200,
+        content=ErrorResponse.create(
+            code=StatusCode.BAD_REQUEST,
+            msg=f"Request parameter validation failed: {'; '.join([f'{e["field"]}: {e["message"]}' for e in error_details])}",
+        ).dict(),
+    )
+
+
+async def general_exception_handler(request: Request, exc: Exception) -> JSONResponse:
+    """General exception handler."""
+    return JSONResponse(
+        status_code=200,
+        content=ErrorResponse.create(
+            code=StatusCode.INTERNAL_ERROR,
+            msg="Internal server error, please try again later",
+        ).dict(),
+    )
diff --git a/python/valuecell/server/api/routers/__init__.py b/python/valuecell/server/api/routers/__init__.py
index e69de29bb..3e64b20fc 100644
--- a/python/valuecell/server/api/routers/__init__.py
+++ b/python/valuecell/server/api/routers/__init__.py
@@ -0,0 +1,8 @@
+"""API router module."""
+
+from .i18n import create_i18n_router, get_i18n_router
+
+__all__ = [
+    "create_i18n_router",
+    "get_i18n_router",
+]
diff --git a/python/valuecell/server/api/routers/i18n.py b/python/valuecell/server/api/routers/i18n.py
new file mode 100644
index 000000000..3b7eb9d78
--- /dev/null
+++ b/python/valuecell/server/api/routers/i18n.py
@@ -0,0 +1,48 @@
+"""RESTful i18n API router module."""
+
+from fastapi import APIRouter
+from ..i18n_api import get_i18n_api
+
+
+def create_i18n_router() -> APIRouter:
+    """Create RESTful style i18n router.
+
+    API path design:
+    - GET /api/v1/i18n/config - Get i18n configuration
+    - GET /api/v1/i18n/languages - Get supported languages list
+    - PUT /api/v1/i18n/language - Set language
+    - GET /api/v1/i18n/timezones - Get supported timezones list
+    - PUT /api/v1/i18n/timezone - Set timezone
+    - POST /api/v1/i18n/language/detect - Detect language
+    - POST /api/v1/i18n/translate - Translate text
+    - POST /api/v1/i18n/format/datetime - Format datetime
+    - POST /api/v1/i18n/format/number - Format number
+    - POST /api/v1/i18n/format/currency - Format currency
+    - GET /api/v1/i18n/users/{user_id}/settings - Get user i18n settings
+    - PUT /api/v1/i18n/users/{user_id}/settings - Update user i18n settings
+    - GET /api/v1/i18n/agents/context - Get Agent i18n context
+
+    Returns:
+        APIRouter: Configured i18n router
+    """
+    # Get existing i18n router, but modify prefix to comply with RESTful style
+    i18n_api = get_i18n_api()
+    router = i18n_api.router
+
+    # Update router prefix to comply with RESTful API versioning
+    router.prefix = "/api/v1/i18n"
+
+    return router
+
+
+def get_i18n_router() -> APIRouter:
+    """Get i18n router instance (backward compatible).
+
+    Returns:
+        APIRouter: Configured i18n router
+    """
+    return create_i18n_router()
+
+
+# Export the router functions
+__all__ = ["create_i18n_router", "get_i18n_router"]
diff --git a/python/valuecell/server/api/schemas/__init__.py b/python/valuecell/server/api/schemas/__init__.py
index e69de29bb..fbb867382 100644
--- a/python/valuecell/server/api/schemas/__init__.py
+++ b/python/valuecell/server/api/schemas/__init__.py
@@ -0,0 +1,63 @@
+"""API schemas package."""
+
+from .base import (
+    StatusCode,
+    BaseResponse,
+    SuccessResponse,
+    ErrorResponse,
+    AppInfoData,
+    HealthCheckData,
+)
+from .i18n import (
+    I18nConfigData,
+    SupportedLanguage,
+    SupportedLanguagesData,
+    TimezoneInfo,
+    TimezonesData,
+    LanguageRequest,
+    TimezoneRequest,
+    LanguageDetectionRequest,
+    TranslationRequest,
+    DateTimeFormatRequest,
+    NumberFormatRequest,
+    CurrencyFormatRequest,
+    UserI18nSettingsData,
+    UserI18nSettingsRequest,
+    AgentI18nContextData,
+    LanguageDetectionData,
+    TranslationData,
+    DateTimeFormatData,
+    NumberFormatData,
+    CurrencyFormatData,
+)
+
+__all__ = [
+    # Base schemas
+    "StatusCode",
+    "BaseResponse",
+    "SuccessResponse",
+    "ErrorResponse",
+    "AppInfoData",
+    "HealthCheckData",
+    # I18n schemas
+    "I18nConfigData",
+    "SupportedLanguage",
+    "SupportedLanguagesData",
+    "TimezoneInfo",
+    "TimezonesData",
+    "LanguageRequest",
+    "TimezoneRequest",
+    "LanguageDetectionRequest",
+    "TranslationRequest",
+    "DateTimeFormatRequest",
+    "NumberFormatRequest",
+    "CurrencyFormatRequest",
+    "UserI18nSettingsData",
+    "UserI18nSettingsRequest",
+    "AgentI18nContextData",
+    "LanguageDetectionData",
+    "TranslationData",
+    "DateTimeFormatData",
+    "NumberFormatData",
+    "CurrencyFormatData",
+]
diff --git a/python/valuecell/server/api/schemas/base.py b/python/valuecell/server/api/schemas/base.py
new file mode 100644
index 000000000..46652f596
--- /dev/null
+++ b/python/valuecell/server/api/schemas/base.py
@@ -0,0 +1,74 @@
+"""Base API schemas for ValueCell application."""
+
+from typing import Optional, Generic, TypeVar
+from datetime import datetime
+from enum import IntEnum
+from pydantic import BaseModel, Field
+
+T = TypeVar("T")
+
+
+class StatusCode(IntEnum):
+    """Unified API status code enumeration."""
+
+    # Success status codes
+    SUCCESS = 0
+
+    # Client error status codes
+    BAD_REQUEST = 400  # Bad request parameters
+    UNAUTHORIZED = 401  # Unauthorized access
+    FORBIDDEN = 403  # Forbidden access
+    NOT_FOUND = 404  # Resource not found
+
+    # Server error status codes
+    INTERNAL_ERROR = 500  # Internal server error
+
+
+class BaseResponse(BaseModel, Generic[T]):
+    """Unified API response base model."""
+
+    code: int = Field(..., description="Status code")
+    msg: str = Field(..., description="Response message")
+    data: Optional[T] = Field(None, description="Response data")
+
+
+class SuccessResponse(BaseResponse[T]):
+    """Success response model."""
+
+    code: int = Field(default=StatusCode.SUCCESS, description="Success status code")
+    msg: str = Field(default="success", description="Success message")
+
+    @classmethod
+    def create(cls, data: T = None, msg: str = "success") -> "SuccessResponse[T]":
+        """Create success response."""
+        return cls(code=StatusCode.SUCCESS, msg=msg, data=data)
+
+
+class ErrorResponse(BaseResponse[None]):
+    """Error response model."""
+
+    code: int = Field(..., description="Error status code")
+    msg: str = Field(..., description="Error message")
+    data: None = Field(default=None, description="Data is null for errors")
+
+    @classmethod
+    def create(cls, code: StatusCode, msg: str) -> "ErrorResponse":
+        """Create error response."""
+        return cls(code=code, msg=msg, data=None)
+
+
+# Common data response models
+class AppInfoData(BaseModel):
+    """Application information data."""
+
+    name: str = Field(..., description="Application name")
+    version: str = Field(..., description="Application version")
+    environment: str = Field(..., description="Runtime environment")
+
+
+class HealthCheckData(BaseModel):
+    """Health check data."""
+
+    status: str = Field(..., description="Service status")
+    version: str = Field(..., description="Service version")
+    timestamp: Optional[datetime] = Field(None, description="Check timestamp")
diff --git a/python/valuecell/server/api/schemas/i18n.py b/python/valuecell/server/api/schemas/i18n.py
new file mode 100644
index 000000000..9ff0206e6
--- /dev/null
+++ b/python/valuecell/server/api/schemas/i18n.py
@@ -0,0 +1,199 @@
+"""I18n related API schemas for ValueCell application."""
+
+from typing import Dict, Any, List, Optional
+from datetime import datetime
+from pydantic import BaseModel, Field, validator
+
+from ...core.constants import SUPPORTED_LANGUAGE_CODES
+
+
+# I18n related data models
+class I18nConfigData(BaseModel):
+    """I18n configuration data model."""
+
+    language: str = Field(..., description="Current language")
+    timezone: str = Field(..., description="Current timezone")
+    date_format: str = Field(..., description="Date format")
+    time_format: str = Field(..., description="Time format")
+    datetime_format: str = Field(..., description="DateTime format")
+    currency_symbol: str = Field(..., description="Currency symbol")
+    number_format: Dict[str, str] = Field(..., description="Number format")
+    is_rtl: bool = Field(..., description="Whether text is right-to-left")
+
+
+class SupportedLanguage(BaseModel):
+    """Supported language schema."""
+
+    code: str = Field(..., description="Language code")
+    name: str = Field(..., description="Language name")
+    is_current: bool = Field(..., description="Whether this is the current language")
+
+
+class SupportedLanguagesData(BaseModel):
+    """Supported languages data."""
+
+    languages: List[SupportedLanguage] = Field(
+        ..., description="List of supported languages"
+    )
+    current: str = Field(..., description="Current language code")
+
+
+class TimezoneInfo(BaseModel):
+    """Timezone information schema."""
+
+    value: str = Field(..., description="Timezone value")
+    label: str = Field(..., description="Timezone display name")
+    is_current: bool = Field(..., description="Whether this is the current timezone")
+
+
+class TimezonesData(BaseModel):
+    """Timezones data."""
+
+    timezones: List[TimezoneInfo] = Field(..., description="List of timezones")
+    current: str = Field(..., description="Current timezone")
+
+
+# API request models
+class LanguageRequest(BaseModel):
+    """Language change request."""
+
+    language: str = Field(..., description="Language code to set")
+
+    @validator("language")
+    def validate_language(cls, v):
+        if v not in SUPPORTED_LANGUAGE_CODES:
+            raise ValueError(f"Language {v} is not supported")
+        return v
+
+
+class TimezoneRequest(BaseModel):
+    """Timezone change request."""
+
+    timezone: str = Field(..., description="Timezone to set")
+
+
+class LanguageDetectionRequest(BaseModel):
+    """Language detection request."""
+
+    accept_language: str = Field(..., description="Accept-Language header value")
+
+
+class TranslationRequest(BaseModel):
+    """Translation request."""
+
+    key: str = Field(..., description="Translation key")
+    language: Optional[str] = Field(None, description="Target language")
+    variables: Optional[Dict[str, Any]] = Field(
+        default_factory=dict, description="Variables for string formatting"
+    )
+
+
+class DateTimeFormatRequest(BaseModel):
+    """DateTime formatting request."""
+
+    datetime: str = Field(..., description="ISO datetime string")
+    format_type: str = Field(
+        "datetime", description="Format type: date, time, or datetime"
+    )
+
+
+class NumberFormatRequest(BaseModel):
+    """Number formatting request."""
+
+    number: float = Field(..., description="Number to format")
+    decimal_places: int = Field(2, description="Number of decimal places")
+
+
+class CurrencyFormatRequest(BaseModel):
+    """Currency formatting request."""
+
+    amount: float = Field(..., description="Amount to format")
+    decimal_places: int = Field(2, description="Number of decimal places")
+
+
+class UserI18nSettingsData(BaseModel):
+    """User i18n settings data."""
+
+    user_id: Optional[str] = Field(None, description="User ID")
+    language: str = Field(default="en-US", description="User language")
+    timezone: str = Field(default="UTC", description="User timezone")
+    created_at: Optional[datetime] = Field(None, description="Creation timestamp")
+    updated_at: Optional[datetime] = Field(None, description="Update timestamp")
+
+    @validator("language")
+    def validate_language(cls, v):
+        if v not in SUPPORTED_LANGUAGE_CODES:
+            raise ValueError(f"Language {v} is not supported")
+        return v
+
+
+class UserI18nSettingsRequest(BaseModel):
+    """User i18n settings update request."""
+
+    language: Optional[str] = Field(None, description="Language to update")
+    timezone: Optional[str] = Field(None, description="Timezone to update")
+
+    @validator("language")
+    def validate_language(cls, v):
+        if v and v not in SUPPORTED_LANGUAGE_CODES:
+            raise ValueError(f"Language {v} is not supported")
+        return v
+
+
+class AgentI18nContextData(BaseModel):
+    """Agent i18n context data for inter-agent communication."""
+
+    language: str = Field(..., description="Language")
+    timezone: str = Field(..., description="Timezone")
+    currency_symbol: str = Field(..., description="Currency symbol")
+    date_format: str = Field(..., description="Date format")
+    time_format: str = Field(..., description="Time format")
+    number_format: Dict[str, str] = Field(..., description="Number format")
+    user_id: Optional[str] = Field(None, description="User ID")
+    session_id: Optional[str] = Field(None, description="Session ID")
+
+
+class LanguageDetectionData(BaseModel):
+    """Language detection result data."""
+
+    detected_language: str = Field(..., description="Detected language")
+    language_name: str = Field(..., description="Language name")
+    is_supported: bool = Field(..., description="Whether the language is supported")
+
+
+class TranslationData(BaseModel):
+    """Translation result data."""
+
+    key: str = Field(..., description="Translation key")
+    translated_text: str = Field(..., description="Translated text")
+    language: str = Field(..., description="Target language")
+    variables: Dict[str, Any] = Field(default_factory=dict, description="Variables")
+
+
+class DateTimeFormatData(BaseModel):
+    """DateTime formatting result data."""
+
+    original: str = Field(..., description="Original datetime")
+    formatted: str = Field(..., description="Formatted datetime")
+    format_type: str = Field(..., description="Format type")
+    language: str = Field(..., description="Language")
+    timezone: str = Field(..., description="Timezone")
+
+
+class NumberFormatData(BaseModel):
+    """Number formatting result data."""
+
+    original: float = Field(..., description="Original number")
+    formatted: str = Field(..., description="Formatted number")
+    decimal_places: int = Field(..., description="Number of decimal places")
+    language: str = Field(..., description="Language")
+
+
+class CurrencyFormatData(BaseModel):
+    """Currency formatting result data."""
+
+    original: float = Field(..., description="Original amount")
+    formatted: str = Field(..., description="Formatted amount")
+    decimal_places: int = Field(..., description="Number of decimal places")
+    language: str = Field(..., description="Language")
+    currency_symbol: str = Field(..., description="Currency symbol")