fix(tools): make NL2SQLTool schema introspection dialect-aware

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Summary

Related to #7782.

This PR fixes a SQLite initialization blocker by replacing PostgreSQL-specific
schema queries with SQLAlchemy reflection.

Dialect-specific SQL-generation guidance remains outstanding under #7782.

NL2SQLTool currently uses PostgreSQL-specific information_schema queries for schema introspection, which causes SQLite databases to fail during initialization.

This change makes schema introspection dialect-aware by using SQLAlchemy inspection APIs for table and column discovery.

Changes

• Use SQLAlchemy inspection for table discovery.
• Use SQLAlchemy inspection for column discovery.
• Preserve the existing table/column data structures.
• Render reflected types using the active SQLAlchemy dialect.
• Handle untyped/reflected columns safely with an UNKNOWN fallback.
• Preserve PostgreSQL public-schema, view, and foreign-table behavior.
• Add SQLite and PostgreSQL-focused regression coverage.
• Strengthen security and resource-cleanup tests.
• Update related documentation/comments.

Verification

• SQLite regression tests pass.
• PostgreSQL compatibility is covered by unit tests.
• Live PostgreSQL tests are opt-in through CREWAI_TEST_PG_URI.
• Mypy passes for the changed code/tests.
• Ruff formatting/checks are clean relative to the repository baseline.
• git diff --check passes.

The remaining Windows WinError 32 failure is pre-existing and tracked separately under #7443; this PR does not change that behavior.

AI disclosure

This contribution was developed with AI-assisted tooling, with the implementation independently reviewed and tested before submission.

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Note

Medium Risk
Changes how every NL2SQLTool instance loads schema metadata at construction time, including PostgreSQL type string formatting; regressions could break agents that depend on exact metadata, though behavior is heavily tested.

Overview
NL2SQLTool no longer bootstraps schema metadata with PostgreSQL-only information_schema SQL. Table and column discovery now goes through SQLAlchemy reflection so SQLite and other dialects can initialize, while keeping the same tables / columns shape.

Initialization reflects the full schema on one short-lived engine: failures raise clear RuntimeErrors, engines are always disposed, and partial metadata is not published if column reflection fails. For PostgreSQL, discovery still targets the public schema and now includes views and foreign tables; elsewhere the dialect default schema is used. Reflected column data_type strings come from compiling SQLAlchemy types (with UNKNOWN when compilation fails), which may differ from old information_schema wording.

Security tests now assert catalogue names are passed to the inspector as arguments, not via execute_sql. A large test_nl2sql_dialect.py suite covers SQLite, mocked PostgreSQL reflection, engine cleanup, and optional live Postgres via CREWAI_TEST_PG_URI.

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• lib/crewai-tools/src/crewai_tools/tools/nl2sql/nl2sql_tool.py
• lib/crewai-tools/tests/tools/test_nl2sql_dialect.py

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📝 Walkthrough

Walkthrough

NL2SQLTool now uses SQLAlchemy reflection to discover tables and columns. PostgreSQL discovery uses the public schema and includes tables, views, and foreign tables. Column types are compiled for the connected dialect. Regression tests cover reflection, query behavior, errors, and engine disposal.

Changes

Database schema reflection

Layer / File(s)	Summary
Reflect schema objects and columns lib/crewai-tools/src/crewai_tools/tools/nl2sql/nl2sql_tool.py	Initialization reflects tables and columns with one engine and inspector. PostgreSQL discovery uses the public schema and includes tables, views, and foreign tables. Column types use dialect compilation, with UNKNOWN when compilation fails.
Verify dialect-specific reflection lib/crewai-tools/tests/tools/test_nl2sql_dialect.py	Tests cover SQLite schema metadata and query behavior, mocked PostgreSQL discovery and type rendering, and optional live PostgreSQL reflection.
Verify errors and engine lifecycle lib/crewai-tools/tests/tools/test_nl2sql_dialect.py, lib/crewai-tools/tests/tools/test_nl2sql_security.py	Tests cover reflection failures, prevention of partial metadata publication, engine and connection lifecycle, and hostile identifiers passed to inspection without SQL execution.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to c78c6

Schema discovery now uses SQLAlchemy reflection across the described SQLite and PostgreSQL paths, with regression coverage for metadata, failures, and cleanup. No concrete remaining behavior or operational risk is identified, so the change is ready to merge.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to c78c6

Dialect-aware reflection fixes SQLite initialization, but it may change which database objects appear in tool metadata. One object that cannot be reflected can also prevent the entire tool from starting. Query permissions remain in place; the remaining risk concerns metadata visibility and failure containment.

Retained concerns

• Medium · security · inferred: Reflection may publish metadata for public-schema objects that the previous privilege-filtered table listing did not enumerate. Whether this occurs for a restricted PostgreSQL role, and who receives that metadata, remains unverified.
• Low · reliability · observed: A column-reflection failure for one discovered object now aborts initialization for the whole tool, rather than leaving an error in that object's column metadata. This reduces failure containment when a schema contains an unreflectable object.

Security review details

Security Blast Radius

• inferred — Potential metadata exposure is bounded by objects visible to inspection through the configured database connection and by consumers receiving tool metadata; no wider deployment or tenant scope is established.

Security Findings and Attack Paths

• inferred — If inspection enumerates an object excluded by the former privilege-filtered listing, its name and column metadata may reach a tool consumer. The evidence does not establish that such an object is exposed in a production configuration or that query access is gained.

Trust Boundaries and Controls

• observed — Reflection does not call the tool's execute_sql method, and SQL-like table identifiers in the SQLite regression test leave an existing table queryable. User-supplied SQL still follows validation before execution under the configured database identity.

Resilience and Maintainability Implications

• observed — An initial column-reflection failure does not publish partial metadata and does dispose the owned engine, although it prevents the entire tool from initializing.

Hardening Proposals

• proposed — Compare reflected object metadata under a restricted PostgreSQL role against the previous listing, and establish which tool consumers receive that metadata before relying on equivalent visibility.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 41.18% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 34 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: making NL2SQLTool schema introspection dialect-aware.
Description check	✅ Passed	The description explains the problem, solution, scope, testing, compatibility considerations, and related issue. It provides verification details, although it does not reproduce every template heading…

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Inline comments:
Review comments at
@lib/crewai-tools/src/crewai_tools/tools/nl2sql/nl2sql_tool.py:
- Around line 446-466: Update model_post_init to create one SQLAlchemy engine
and inspector for the full reflection pass, reuse them for table discovery and
each table’s column query, and dispose the engine when initialization finishes.
Keep _fetch_available_tables and _fetch_all_available_columns signatures and
return/error contracts as wrappers around private inspector-based helpers;
retain a separate column query for every discovered table.

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📒 Files selected for processing (3)

• lib/crewai-tools/src/crewai_tools/tools/nl2sql/nl2sql_tool.py
• lib/crewai-tools/tests/tools/test_nl2sql_dialect.py
• lib/crewai-tools/tests/tools/test_nl2sql_security.py

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