docs: Document arguments and returns for utility and filter functions

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/common/binary_detection.rs

@@ -4,6 +4,19 @@ use axum::http::StatusCode;
 use std::collections::HashMap;
 
 /// Check if content is binary when allow_binary is false
+///
+/// # Arguments
+///
+/// * `item_service` - Reference to the async item service
+/// * `item_id` - The ID of the item to check
+/// * `metadata` - Metadata associated with the item
+/// * `allow_binary` - Whether binary content is allowed
+///
+/// # Returns
+///
+/// * `Result<(), StatusCode>` - 
+///     * `Ok(())` if binary content is allowed or content is not binary
+///     * `Err(StatusCode::BAD_REQUEST)` if binary content is not allowed and content is binary
 pub async fn check_binary_content_allowed(
     item_service: &AsyncItemService,
     item_id: i64,
@@ -20,6 +33,19 @@ pub async fn check_binary_content_allowed(
 }
 
 /// Helper function to determine if content is binary
+///
+/// # Arguments
+///
+/// * `item_service` - Reference to the async item service
+/// * `item_id` - The ID of the item to check
+/// * `metadata` - Metadata associated with the item
+///
+/// # Returns
+///
+/// * `Result<bool, StatusCode>` - 
+///     * `Ok(true)` if content is binary
+///     * `Ok(false)` if content is text
+///     * `Err(StatusCode)` if an error occurs during checking
 pub async fn is_content_binary(
     item_service: &AsyncItemService,
     item_id: i64,