fix(tools): make NL2SQL guidance dialect-aware

lib/crewai-tools/src/crewai_tools/tools/nl2sql/README.md

@@ -61,6 +61,14 @@ def researcher(self) -> Agent:
     )
 ```
 
+The tool infers the SQL dialect from `db_uri` and includes dialect-specific
+query-generation guidance for the agent. You can override the detected dialect
+when needed:
+
+```python
+nl2sql = NL2SQLTool(db_uri="sqlite:///example.db", dialect="sqlite")
+```
+
 ## Example
 
 The primary task goal was:

lib/crewai-tools/src/crewai_tools/tools/nl2sql/nl2sql_tool.py

@@ -16,6 +16,7 @@
 
 try:
     from sqlalchemy import create_engine, text
+    from sqlalchemy.engine import make_url
     from sqlalchemy.orm import sessionmaker
 
     SQLALCHEMY_AVAILABLE = True
@@ -24,6 +25,19 @@
 
 logger = logging.getLogger(__name__)
 
+_DIALECT_GUIDANCE = {
+    "postgresql": (
+        "Generate PostgreSQL-compatible SQL. PostgreSQL features such as ILIKE, "
+        "DATE_TRUNC, INTERVAL, and :: casts are available."
+    ),
+    "sqlite": (
+        "Generate SQLite-compatible SQL. Use LOWER(column) LIKE LOWER(pattern) "
+        "for case-insensitive matching, SQLite date/time functions such as "
+        "strftime(), and || for string concatenation. Do not use ILIKE, "
+        "DATE_TRUNC, INTERVAL, or :: casts."
+    ),
+}
+
 # Commands allowed in read-only mode
 # NOTE: WITH is intentionally excluded — writable CTEs start with WITH, so the
 # CTE body must be inspected separately (see _validate_statement).
@@ -237,6 +251,14 @@ class NL2SQLTool(BaseTool):
         title="Database URI",
         description="The URI of the database to connect to.",
     )
+    dialect: str | None = Field(
+        default=None,
+        title="SQL Dialect",
+        description=(
+            "SQL dialect used when generating queries. Inferred from db_uri when "
+            "not provided."
+        ),
+    )
     allow_dml: bool = Field(
         default=False,
         title="Allow DML",
@@ -269,6 +291,18 @@ def model_post_init(self, __context: Any) -> None:
                 "`pip install crewai-tools[sqlalchemy]`"
             )
 
+        self.dialect = (
+            self.dialect.strip().lower()
+            if self.dialect and self.dialect.strip()
+            else make_url(self.db_uri).get_backend_name()
+        )
+        guidance = _DIALECT_GUIDANCE.get(
+            self.dialect,
+            f"Generate SQL compatible with the {self.dialect} dialect.",
+        )
+        if guidance not in self.description:
+            self.description = f"{self.description.rstrip()} {guidance}"
+
         if self.allow_dml:
             logger.warning(
                 "NL2SQLTool: allow_dml=True — write operations (INSERT/UPDATE/"

lib/crewai-tools/tests/tools/test_nl2sql_dialect_guidance.py

@@ -0,0 +1,61 @@
+"""Tests for dialect-specific NL2SQLTool generation guidance."""
+
+from unittest.mock import patch
+
+import pytest
+
+
+pytest.importorskip("sqlalchemy")
+
+from crewai_tools.tools.nl2sql.nl2sql_tool import NL2SQLTool  # noqa: E402
+
+
+def _make_tool(db_uri: str, **kwargs: object) -> NL2SQLTool:
+    with (
+        patch.object(NL2SQLTool, "_fetch_available_tables", return_value=[]),
+        patch.object(NL2SQLTool, "_fetch_all_available_columns", return_value=[]),
+    ):
+        return NL2SQLTool(db_uri=db_uri, **kwargs)
+
+
+def test_sqlite_dialect_is_inferred_from_uri() -> None:
+    tool = _make_tool("sqlite:///example.db")
+
+    assert tool.dialect == "sqlite"
+    assert "Generate SQLite-compatible SQL" in tool.description
+    assert "Do not use ILIKE" in tool.description
+
+
+def test_postgresql_dialect_is_inferred_from_uri() -> None:
+    tool = _make_tool("postgresql://user:password@localhost/database")
+
+    assert tool.dialect == "postgresql"
+    assert "Generate PostgreSQL-compatible SQL" in tool.description
+    assert "ILIKE" in tool.description
+
+
+def test_explicit_dialect_overrides_uri() -> None:
+    tool = _make_tool(
+        "postgresql://user:password@localhost/database", dialect=" SQLite "
+    )
+
+    assert tool.dialect == "sqlite"
+    assert "Generate SQLite-compatible SQL" in tool.description
+
+
+def test_custom_description_is_preserved() -> None:
+    tool = _make_tool(
+        "sqlite:///example.db",
+        description="Use the reporting database.",
+    )
+
+    assert tool.description.startswith("Use the reporting database.")
+    assert "Generate SQLite-compatible SQL" in tool.description
+
+
+def test_dialect_guidance_is_not_duplicated_on_restore() -> None:
+    tool = _make_tool("sqlite:///example.db")
+
+    restored = _make_tool(**tool.model_dump())
+
+    assert restored.description.count("Generate SQLite-compatible SQL") == 1