Fix: Correct MCP catalog JSON parsing to handle special characters

The catalog_search() and catalog_list() methods in MySQL_Catalog.cpp
were manually building JSON strings by concatenating raw TEXT from
SQLite without proper escaping. This caused parse errors when stored
JSON contained quotes, backslashes, or newlines.

Changes:
- MySQL_Catalog.cpp: Use nlohmann::json to build proper nested JSON
  in search() and list() methods instead of manual concatenation
- MySQL_Tool_Handler.cpp: Add try-catch for JSON parsing in catalog_get()
- test_catalog.sh: Fix MCP URL path, add jq extraction for MCP protocol
  responses, add 3 special character tests (CAT013-CAT015)

Test Results: All 15 catalog tests pass, including new tests that
verify special characters (quotes, backslashes) are preserved.

lib/MySQL_Catalog.cpp

@@ -3,6 +3,7 @@
 #include "proxysql.h"
 #include <sstream>
 #include <algorithm>
+#include "../deps/json/json.hpp"
 
 MySQL_Catalog::MySQL_Catalog(const std::string& path)
 	: db(NULL), db_path(path)
@@ -220,31 +221,40 @@ std::string MySQL_Catalog::search(
 		return "[]";
 	}
 
-	// Build JSON result
-	std::ostringstream json;
-	json << "[";
-	bool first = true;
+	// Build JSON result using nlohmann::json
+	nlohmann::json results = nlohmann::json::array();
 
 	if (resultset) {
 		for (std::vector<SQLite3_row*>::iterator it = resultset->rows.begin();
 		     it != resultset->rows.end(); ++it) {
 			SQLite3_row* row = *it;
-			if (!first) json << ",";
-			first = false;
-
-			json << "{"
-			     << "\"kind\":\"" << (row->fields[0] ? row->fields[0] : "") << "\","
-			     << "\"key\":\"" << (row->fields[1] ? row->fields[1] : "") << "\","
-			     << "\"document\":" << (row->fields[2] ? row->fields[2] : "null") << ","
-			     << "\"tags\":\"" << (row->fields[3] ? row->fields[3] : "") << "\","
-			     << "\"links\":\"" << (row->fields[4] ? row->fields[4] : "") << "\""
-			     << "}";
+
+			nlohmann::json entry;
+			entry["kind"] = std::string(row->fields[0] ? row->fields[0] : "");
+			entry["key"] = std::string(row->fields[1] ? row->fields[1] : "");
+
+			// Parse the stored JSON document - nlohmann::json handles escaping
+			const char* doc_str = row->fields[2];
+			if (doc_str) {
+				try {
+					entry["document"] = nlohmann::json::parse(doc_str);
+				} catch (const nlohmann::json::parse_error& e) {
+					// If document is not valid JSON, store as string
+					entry["document"] = std::string(doc_str);
+				}
+			} else {
+				entry["document"] = nullptr;
+			}
+
+			entry["tags"] = std::string(row->fields[3] ? row->fields[3] : "");
+			entry["links"] = std::string(row->fields[4] ? row->fields[4] : "");
+
+			results.push_back(entry);
 		}
 		delete resultset;
 	}
 
-	json << "]";
-	return json.str();
+	return results.dump();
 }
 
 std::string MySQL_Catalog::list(
@@ -282,31 +292,42 @@ std::string MySQL_Catalog::list(
 	resultset = NULL;
 	db->execute_statement(sql.str().c_str(), &error, &cols, &affected, &resultset);
 
-	// Build JSON result with total count
-	std::ostringstream json;
-	json << "{\"total\":" << total << ",\"results\":[";
+	// Build JSON result using nlohmann::json
+	nlohmann::json result;
+	result["total"] = total;
+	nlohmann::json results = nlohmann::json::array();
 
-	bool first = true;
 	if (resultset) {
 		for (std::vector<SQLite3_row*>::iterator it = resultset->rows.begin();
 		     it != resultset->rows.end(); ++it) {
 			SQLite3_row* row = *it;
-			if (!first) json << ",";
-			first = false;
-
-			json << "{"
-			     << "\"kind\":\"" << (row->fields[0] ? row->fields[0] : "") << "\","
-			     << "\"key\":\"" << (row->fields[1] ? row->fields[1] : "") << "\","
-			     << "\"document\":" << (row->fields[2] ? row->fields[2] : "null") << ","
-			     << "\"tags\":\"" << (row->fields[3] ? row->fields[3] : "") << "\","
-			     << "\"links\":\"" << (row->fields[4] ? row->fields[4] : "") << "\""
-			     << "}";
+
+			nlohmann::json entry;
+			entry["kind"] = std::string(row->fields[0] ? row->fields[0] : "");
+			entry["key"] = std::string(row->fields[1] ? row->fields[1] : "");
+
+			// Parse the stored JSON document
+			const char* doc_str = row->fields[2];
+			if (doc_str) {
+				try {
+					entry["document"] = nlohmann::json::parse(doc_str);
+				} catch (const nlohmann::json::parse_error& e) {
+					entry["document"] = std::string(doc_str);
+				}
+			} else {
+				entry["document"] = nullptr;
+			}
+
+			entry["tags"] = std::string(row->fields[3] ? row->fields[3] : "");
+			entry["links"] = std::string(row->fields[4] ? row->fields[4] : "");
+
+			results.push_back(entry);
 		}
 		delete resultset;
 	}
 
-	json << "]}";
-	return json.str();
+	result["results"] = results;
+	return result.dump();
 }
 
 int MySQL_Catalog::merge(

lib/MySQL_Tool_Handler.cpp

@@ -910,7 +910,13 @@ std::string MySQL_Tool_Handler::catalog_get(const std::string& kind, const std::
 	if (rc == 0) {
 		result["kind"] = kind;
 		result["key"] = key;
-		result["document"] = json::parse(document);
+		// Parse as raw JSON value to preserve nested structure
+		try {
+			result["document"] = json::parse(document);
+		} catch (const json::parse_error& e) {
+			// If not valid JSON, store as string
+			result["document"] = document;
+		}
 	} else {
 		result["error"] = "Entry not found";
 	}

scripts/mcp/test_catalog.sh

@@ -15,7 +15,7 @@ set -e
 # Configuration
 MCP_HOST="${MCP_HOST:-127.0.0.1}"
 MCP_PORT="${MCP_PORT:-6071}"
-MCP_URL="https://${MCP_HOST}:${MCP_PORT}/query"
+MCP_URL="https://${MCP_HOST}:${MCP_PORT}/mcp/query"
 
 # Test options
 VERBOSE=false
@@ -39,7 +39,7 @@ log_test() {
     echo -e "${BLUE}[TEST]${NC} $1"
 }
 
-# Execute MCP request
+# Execute MCP request and unwrap response
 mcp_request() {
     local payload="$1"
 
@@ -48,7 +48,16 @@ mcp_request() {
         -H "Content-Type: application/json" \
         -d "${payload}" 2>/dev/null)
 
-    echo "${response}"
+    # Extract content from MCP protocol wrapper if present
+    # MCP format: {"result":{"content":[{"text":"..."}]}}
+    local extracted
+    extracted=$(echo "${response}" | jq -r 'if .result.content[0].text then .result.content[0].text else . end' 2>/dev/null)
+
+    if [ -n "${extracted}" ] && [ "${extracted}" != "null" ]; then
+        echo "${extracted}"
+    else
+        echo "${response}"
+    fi
 }
 
 # Test catalog operations
@@ -290,6 +299,72 @@ run_catalog_tests() {
         failed=$((failed + 1))
     fi
 
+    # Test 13: Special characters in document (JSON parsing bug test)
+    local payload13
+    payload13='{
+  "jsonrpc": "2.0",
+  "method": "tools/call",
+  "params": {
+    "name": "catalog_upsert",
+    "arguments": {
+      "kind": "test",
+      "key": "special_chars",
+      "document": "{\"description\": \"Test with \\\"quotes\\\" and \\\\backslashes\\\\\"}",
+      "tags": "test,special",
+      "links": ""
+    }
+  },
+  "id": 13
+}'
+
+    if test_catalog "CAT013" "Upsert special characters" "${payload13}" '"success"[[:space:]]*:[[:space:]]*true'; then
+        passed=$((passed + 1))
+    else
+        failed=$((failed + 1))
+    fi
+
+    # Test 14: Verify special characters can be read back
+    local payload14
+    payload14='{
+  "jsonrpc": "2.0",
+  "method": "tools/call",
+  "params": {
+    "name": "catalog_get",
+    "arguments": {
+      "kind": "test",
+      "key": "special_chars"
+    }
+  },
+  "id": 14
+}'
+
+    if test_catalog "CAT014" "Get special chars entry" "${payload14}" 'quotes'; then
+        passed=$((passed + 1))
+    else
+        failed=$((failed + 1))
+    fi
+
+    # Test 15: Cleanup special chars entry
+    local payload15
+    payload15='{
+  "jsonrpc": "2.0",
+  "method": "tools/call",
+  "params": {
+    "name": "catalog_delete",
+    "arguments": {
+      "kind": "test",
+      "key": "special_chars"
+    }
+  },
+  "id": 15
+}'
+
+    if test_catalog "CAT015" "Cleanup special chars" "${payload15}" '"success"[[:space:]]*:[[:space:]]*true'; then
+        passed=$((passed + 1))
+    else
+        failed=$((failed + 1))
+    fi
+
     # Test 10: Delete entry
     local payload10
     payload10='{