fix(graph): improve LLM tool UX for GetSubgraphTool and ReadGraphTool

server/src/handlers/graph.rs

@@ -625,6 +625,7 @@ impl McpTool for ReadGraphHandler {
                 .entities
                 .iter()
                 .filter(|(_, v)| req.namespace.as_ref().is_none_or(|ns| &v.namespace == ns))
+                .filter(|(_, v)| req.entity_type.as_ref().is_none_or(|et| &v.entity_type == et))
                 .collect();
 
             let total_count = filtered_entities.len();
@@ -1120,7 +1121,7 @@ impl McpTool for GetSubgraphHandler {
             crate::error::AppError::Internal("root_entity is required".to_string())
         })?;
         let depth = req.depth.unwrap_or(2);
-        let format = req.format.unwrap_or(SubgraphFormat::Json);
+        let format = req.format.unwrap_or(SubgraphFormat::MarkdownTree);
 
         let (matched_entities, matched_relations) = state.read_graph(|full| {
             let mut adj: std::collections::HashMap<&str, Vec<&str>> =