fix(agentgateway): handle empty MCP tool list

[ricardosrib]

Description

Fixes unexpected errors in agent gateway – LoB and customer flows – when an MCP server returns no tools.

Two issues were addressed:

• Null guard on result.tools: session.list_tools() can return None for tools instead of an empty list. Iterating directly over None raised a TypeError. Added result.tools or [] in both _lob.py and _customer.py to handle both None and empty list safely.
• Info log for empty tool list: When a fragment returns no tools, an info-level log is emitted ("No tools returned by AGW for fragment '...'") so the absence of tools is observable without raising an error.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Dependency update

How to Test

1. Run the unit tests: .venv/bin/pytest tests/agentgateway/unit/test_lob.py::TestListServerTools -v
2. Verify all 3 new test cases pass:
   • test_returns_empty_list_and_logs_when_no_tools — returns [] and emits info log
   • test_returns_tools_with_server_info_name — normal tools returned correctly
   • test_falls_back_to_fragment_name_when_server_info_missing — fallback when serverInfo is absent

Checklist

• I have read the Contributing Guidelines
• I have verified that my changes solve the issue
• I have added/updated automated tests to cover my changes
• All tests pass locally
• I have verified that my code follows the Code Guidelines
• I have updated documentation (if applicable)
• I have added type hints for all public APIs
• My code does not contain sensitive information (credentials, tokens, etc.)
• I have followed Conventional Commits for commit messages

Additional Notes

The fix applies to both _lob.py (LoB flow) and _customer.py (customer flow) since both had the same missing null guard on result.tools.

[tiagoek]

SDK Module Review

Check	Status	Findings
bdd	✅ PASS	0
binding-shape	✅ PASS	0
commits	✅ PASS	0
concurrency	✅ PASS	0
constants	✅ PASS	0
deletion-hygiene	✅ PASS	0
deps-supply	✅ PASS	0
disclosure	✅ PASS	0
docs	✅ PASS	0
errors-logging	⚠️ FLAG	1
hardcode	✅ PASS	0
http-hygiene	✅ PASS	0
license-spdx	✅ PASS	0
patterns	✅ PASS	0
pr-size	✅ PASS	0
quality-gate-parity	✅ PASS	0
secrets	✅ PASS	0
telemetry	✅ PASS	0
testing-depth	✅ PASS	0
versioning	✅ PASS	0

Findings (1)

• [FLAG] PY-EL-02 — except block does not end with raise — swallowing? Add re-raise or comment justifying suppression (inline on src/sap_cloud_sdk/agentgateway/_lob.py:391)

1 finding(s): 1 posted as inline comment(s) on the affected lines, 0 not tied to a code line (listed above).

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