Format massive JSON arrays into Markdown natively to avoid context blowouts

server/src/handlers/graph.rs

@@ -1279,16 +1279,38 @@ impl McpTool for SweepGraphHealthHandler {
             }
         });
 
-        let report = serde_json::json!({
-            "orphaned_entities": orphans,
-            "orphans_pruned": auto_prune,
-            "stale_entities": stale_entities,
-            "stale_pruned": auto_prune_stale,
-            "potential_duplicates": duplicates,
-            "health_score": if orphans.is_empty() && duplicates.is_empty() && stale_entities.is_empty() { "100%" } else { "Needs Maintenance" }
-        });
+        let mut out = String::new();
+        out.push_str("## Graph Health Report\n\n");
+        let score = if orphans.is_empty() && duplicates.is_empty() && stale_entities.is_empty() { "100% (Healthy)" } else { "Needs Maintenance" };
+        out.push_str(&format!("**Health Status:** {}\n\n", score));
 
-        Ok(serde_yaml::to_string(&report)?)
+        out.push_str(&format!("### Orphaned Entities ({})\n", orphans.len()));
+        if auto_prune {
+            out.push_str("*These orphans were automatically pruned.*\n");
+        }
+        for o in orphans {
+            out.push_str(&format!("- `{}`\n", o));
+        }
+        out.push_str("\n");
+
+        out.push_str(&format!("### Stale Entities ({})\n", stale_entities.len()));
+        if auto_prune_stale {
+            out.push_str("*These stale entities were automatically pruned.*\n");
+        }
+        for s in stale_entities {
+            out.push_str(&format!("- `{}`\n", s));
+        }
+        out.push_str("\n");
+
+        out.push_str(&format!("### Potential Duplicates ({})\n", duplicates.len()));
+        for d in duplicates {
+            let a = d.get("entity_a").and_then(|x| x.as_str()).unwrap_or("?");
+            let b = d.get("entity_b").and_then(|x| x.as_str()).unwrap_or("?");
+            let act = d.get("suggested_action").and_then(|x| x.as_str()).unwrap_or("");
+            out.push_str(&format!("- `{}` and `{}`\n  - Suggested: `{}`\n", a, b, act));
+        }
+
+        Ok(out)
     }
 }