wp_head hook by page ID [closed]

If you want to use different meta tags for different pages I recommend you to use custom field values.

If you prefer to do it with conditional functions, try this:

add_action( 'wp_head','carlos_head_meta_page' );  
function carlos_head_meta_page() { 

    if ( is_page('4') ) {
        $description = 'tag1';
    } else {
        $description = 'tag2';
    }
    ?> 
    <meta name="description" content="<?php echo $description ?>" />
    <?php

}