<xsl:template name="translate_entry" match="*/id">
  <xsl:param name="entry_id"/>
  <xsl:value-of select="document( 'descr.xml'
)/entries/entry[@id='$entry_id']"/>

You always retrieve the entry having an id with the string value
'$entry-id'. Just use
  @id=$entry_id
(without the apostrophes)