Fix schema handling in SQLTools for table inspection (#3060)

## Summary

Fixes SQLAlchemy schema handling in the SQLTools class. Currently, the
schema parameter is accepted in the constructor but not properly used
when listing tables or describing table structure. This causes errors
when working with databases where tables exist in non-default schemas
(outside of "public" in PostgreSQL).

## Type of change

- [x] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Improvement
- [ ] Model update
- [ ] Other:

---

## Checklist

- [x] Code complies with style guidelines
- [x] Ran format/validation scripts (`./scripts/format.sh` and
`./scripts/validate.sh`)
- [x] Self-review completed
- [x] Documentation updated (comments, docstrings)
- [ ] Examples and guides: Relevant cookbook examples have been included
or updated (if applicable)
- [x] Tested in clean environment
- [ ] Tests added/updated (if applicable)

---

## Additional Notes

The core issue is that SQLAlchemy defaults to the "public" schema in
PostgreSQL when no schema is specified in the inspector methods. Even
though a schema parameter is provided to the SQLTools constructor, it
wasn't being passed to the underlying inspector calls.
This fix ensures that:
1. When listing tables with `list_tables()`, we properly pass the schema
parameter to `get_table_names()`
2. When describing a table with `describe_table()`, we correctly use the
schema parameter with `get_columns()`
3. Error logging has been improved throughout the class

This resolves the "table not found" errors that occur when working with
databases where tables are located in non-default schemas, such as when
using a schema other than "public" in PostgreSQL.
Tested with PostgreSQL database with tables in custom schemas to verify
the fix works properly.

---------

Co-authored-by: Tiberiu Scarlat <tiberiu.scarlat@arnia.ro>
Co-authored-by: Yash Pratap Solanky <101447028+ysolanky@users.noreply.github.com>

Author: 3 people

libs/agno/agno/tools/sql.py

@@ -49,6 +49,8 @@ def __init__(
         self.db_engine: Engine = _engine
         self.Session: sessionmaker[Session] = sessionmaker(bind=self.db_engine)
 
+        self.schema = schema
+
         # Tables this toolkit can access
         self.tables: Optional[Dict[str, Any]] = tables
 
@@ -71,7 +73,11 @@ def list_tables(self) -> str:
 
         try:
             log_debug("listing tables in the database")
-            table_names = inspect(self.db_engine).get_table_names()
+            inspector = inspect(self.db_engine)
+            if self.schema:
+                table_names = inspector.get_table_names(schema=self.schema)
+            else:
+                table_names = inspector.get_table_names()
             log_debug(f"table_names: {table_names}")
             return json.dumps(table_names)
         except Exception as e:
@@ -90,9 +96,14 @@ def describe_table(self, table_name: str) -> str:
 
         try:
             log_debug(f"Describing table: {table_name}")
-            table_names = inspect(self.db_engine)
-            table_schema = table_names.get_columns(table_name)
-            return json.dumps([str(column) for column in table_schema])
+            inspector = inspect(self.db_engine)
+            table_schema = inspector.get_columns(table_name, schema=self.schema)
+            return json.dumps(
+                [
+                    {"name": column["name"], "type": str(column["type"]), "nullable": column["nullable"]}
+                    for column in table_schema
+                ]
+            )
         except Exception as e:
             logger.error(f"Error getting table schema: {e}")
             return f"Error getting table schema: {e}"