[finklen-amazon]

Fixes a regression from #4939.

Summary

Changes

• billing-conductor, get-billing-group-cost-report: the future-month check added in fix(billing-cost-management-mcp-server): reject or flag future Billing Conductor billing periods #4939 ran re.fullmatch on InclusiveStartBillingPeriod from the caller's billing_period_range JSON. A non-empty non-string value (for example 202701, an object, or true) raised TypeError before any request; empty ones such as 0 or {} already fell through to botocore. _is_future_billing_period now returns False for any non-string value, as its docstring already said for malformed input, so botocore rejects the request with its usual ParamValidationError.
• procurement-preferences tests: the list tests used the Get-shaped sample_preference fixture, which carries EinvoiceDeliveryPreference, a field list summaries never return. They now use a sample_preference_summary fixture built from ProcurementPortalPreferenceSummary members, checked against the botocore model. Get tests are unchanged. Test-only.

No tool parameter, description or success response changes.

User experience

get-billing-group-cost-report with billing_period_range={"InclusiveStartBillingPeriod": 202701, "ExclusiveEndBillingPeriod": "2026-11"}:

• Before: error_type: unknown_typeerror, retry_strategy: do_not_retry, message: "expected string or bytes-like object".
• After: error_type: validation_error, boto_error_type: ParamValidationError, retry_strategy: modify_request, and a message that names BillingPeriodRange.InclusiveStartBillingPeriod and its type. No request is sent.

String starts behave as before: a future month is still refused locally, and current, past and malformed strings are sent to the service.

Testing

• New unit tests: _is_future_billing_period returns False for int, dict, list and bytes, and get_billing_group_cost_report with an int, object or boolean start returns the ParamValidationError from a real botocore client, with a before-send hook proving that nothing is sent. 7 of the 15 tests selected fail on main (the 7 new cases); the other 8 are existing regression guards. The fixture check is a regression guard and passes on main.
• Billing Conductor and procurement-preferences test files: 303 passed; ruff check, ruff format --check and pyright are clean.
• Live check against a real account, calling the served tools over stdio: 11/11 pass on this branch and 7/11 on main. The 4 failures on main are the int and object start cases. The controls (a string start reaches the service; a future string start is still refused locally) and the procurement-preferences list shape checks pass on both.

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Is this a breaking change? (Y/N) N

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.79%. Comparing base (69e2666) to head (6a7e164).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4992   +/-   ##
=======================================
  Coverage   93.79%   93.79%           
=======================================
  Files        1080     1080           
  Lines       94712    94714    +2     
  Branches    15442    15443    +1     
=======================================
+ Hits        88833    88835    +2     
  Misses       3505     3505           
  Partials     2374     2374           

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