Expose database type to MCP clients to prevent wrong SQL dialect

- Add Config.db_type property (detects PostgreSQL/MySQL/SQLite from URL)
- Include db_type in sql.query tool description and resource://config
- Remove duplicated _detect_db_type() from assistant/service.py

Author: loglux

app/assistant/service.py

@@ -44,7 +44,7 @@ async def chat(
         schema_result = self.registry.call("sql.schema", {})
         schema_json = json.dumps(schema_result.get("schema", {}), indent=2)
 
-        db_type = _detect_db_type(self.config.db_url)
+        db_type = self.config.db_type
         system = SYSTEM_PROMPT.format(db_type=db_type, schema=schema_json)
 
         messages: List[Dict[str, Any]] = [{"role": "system", "content": system}]
@@ -94,16 +94,6 @@ def _parse_llm_response(text: str) -> Dict[str, Any]:
     return {"thought": "", "sql": None, "explanation": text}
 
 
-def _detect_db_type(db_url: str) -> str:
-    if "postgresql" in db_url or "postgres" in db_url:
-        return "PostgreSQL"
-    if "mysql" in db_url:
-        return "MySQL"
-    if "sqlite" in db_url:
-        return "SQLite"
-    return "SQL"
-
-
 """
 Supported LLM_PROVIDER values and their base URLs:
 

app/config.py

@@ -118,6 +118,17 @@ def load(cls) -> "Config":
             chat_history_limit=chat_history_limit,
         )
 
+    @property
+    def db_type(self) -> str:
+        url = self.db_url.lower()
+        if "postgresql" in url or "postgres" in url:
+            return "PostgreSQL"
+        if "mysql" in url:
+            return "MySQL"
+        if "sqlite" in url:
+            return "SQLite"
+        return "SQL"
+
     @classmethod
     def from_env(cls) -> "Config":
         return cls.load()

app/mcp/resources.py

@@ -40,6 +40,7 @@ def read_resource(self, uri: str) -> Dict[str, Any]:
             }
         if uri == "resource://config":
             config_summary = {
+                "db_type": self.config.db_type,
                 "mode": self.config.mode,
                 "limit_default": self.config.limit_default,
                 "timeout_ms": self.config.timeout_ms,

app/mcp/tools.py

@@ -385,7 +385,8 @@ def db_migrate_plan_apply(payload: Dict[str, Any]) -> Dict[str, Any]:
                 name="sql.query",
                 title="SQL Query",
                 description=(
-                    "Execute a read-only SQL query. "
+                    f"Execute a read-only SQL query against {config.db_type}. "
+                    f"Use {config.db_type}-compatible syntax. "
                     "Only SELECT, WITH, and EXPLAIN statements are allowed. "
                     "For INSERT, UPDATE, DELETE, or DDL statements use db.apply."
                 ),