@@ -212,7 +212,7 @@ def _with_example_dates(description: str) -> str:
    Required: operation="getSavingsPlansUtilization", start_date, end_date
    Optional: granularity, filter
    Example: {"operation": "getSavingsPlansUtilization", "granularity": "MONTHLY"}
-   Notes: Supports only DAILY and MONTHLY granularity. start_date must be within the last 13 months, and end_date must be before the current date. Data lags ~1 day: a window ending today (an incomplete UTC day) may come back empty or as a DataUnavailableException. A DataUnavailableException here means there is no Savings Plans data for THIS window (no active plans, or the window is outside the plan period) — report none/zero and do NOT retry the identical window; change the window (e.g. set end_date to yesterday) instead.
+   Notes: Supports only DAILY and MONTHLY granularity. start_date must be within the last 13 months, and end_date is exclusive and may be today. Data for the most recent 2-3 days (counting today) is not processed yet: a start_date in those days returns a DataUnavailableException, and a window that reaches into them silently leaves them out; a start_date at least 3 days before today is usually past that delay. A DataUnavailableException here means there is no Savings Plans data for THIS window and filter (the window is too recent, no plan was active in it, or a filter value such as an unknown SAVINGS_PLANS_TYPE matches nothing) — report that no data is available for that window (not zero) and do NOT resend the identical request; correct an unknown filter value, and query an earlier window only if the question allows it.
    Returns: Savings Plans utilization for the specified time period
 
 DIMENSION REFERENCE:
 
@@ -89,6 +89,14 @@
 dimensions and nests one level deep; multiple values for one dimension are OR'd.
 The SERVICE filter defaults to Amazon Elastic Compute Cloud - Compute when omitted.
 
+DATA FRESHNESS: Reserved Instance utilization data for the most recent 2-3 days
+(counting today) is not processed yet. A get_reservation_utilization start_date inside
+those days returns a DataUnavailableException, which the service sends without a
+message. It means there is no data for that window, not a failure and not zero
+utilization: report that, and do not resend the identical request. A start_date at
+least 3 days before today is usually past that delay; query an earlier window only if
+the question allows it.
+
 SCOPING LARGE QUERIES: a grouped or DAILY query over a wide window or many
 subscriptions can exceed the tool result size cap and return a ToolResultOversized
 error. Scope such queries with `filter` (e.g. one SERVICE or one SUBSCRIPTION_ID),
 
@@ -64,12 +64,18 @@
 DATES AND DATA FRESHNESS (all three operations):
 - start_date must be within the last 13 months (the Cost Explorer lookback); an
   older start_date returns a ValidationException.
-- Savings Plans data lags roughly one day. A window whose end_date is today (an
-  incomplete UTC day) commonly comes back as a DataUnavailableException with an
-  empty message. Set end_date to exclude today (end_date is exclusive), then the
-  window resolves. A DataUnavailableException means there is no data for THIS
-  window (no active plans, or the window is outside the plan period); report none
-  and do NOT retry the identical request — change the window instead.
+- Savings Plans data for the most recent 2-3 days (counting today) is not processed
+  yet: yesterday is usually still missing, so excluding only today is not enough. A
+  start_date inside those days returns a DataUnavailableException, which the service
+  sends without a message. A window that only reaches into those days succeeds but
+  silently leaves them out, so the last entry can end before end_date. A start_date at
+  least 3 days before today is usually past that delay.
+- A DataUnavailableException means there is no data for THIS window and filter: the
+  window is too recent, no plan was active in it, or a filter value matches nothing
+  (an unknown SAVINGS_PLANS_TYPE, for example, returns this error, not a
+  ValidationException). Report that no data is available for that window (not zero
+  utilization or coverage) and do NOT resend the identical request. Correct an unknown
+  filter value; query an earlier window only if the question allows it.
 
 UTILIZATION DETAILS filters (get_savings_plans_utilization_details):
 - filter accepts LINKED_ACCOUNT, SAVINGS_PLAN_ARN, REGION, PAYMENT_OPTION,
@@ -126,7 +132,7 @@ async def sp_performance(
         ctx: The MCP context object
         operation: The operation to perform: 'get_savings_plans_coverage', 'get_savings_plans_utilization', or 'get_savings_plans_utilization_details'
         start_date: Start date in YYYY-MM-DD format (inclusive). Defaults to 30 days ago if not provided. Must be within the last 13 months.
-        end_date: End date in YYYY-MM-DD format (exclusive). Defaults to today if not provided. Savings Plans data lags ~1 day; a window ending today may return an empty-message DataUnavailableException, so set end_date to exclude today.
+        end_date: End date in YYYY-MM-DD format (exclusive). Defaults to today if not provided. Savings Plans data for the last 2-3 days (counting today) is not processed yet: a start_date in those days returns a DataUnavailableException, and a window reaching into them leaves them out.
         granularity: Time granularity of the data (DAILY or MONTHLY). Defaults to DAILY. For coverage, ignored when group_by is provided (granularity and group_by are mutually exclusive).
         metrics: List of metrics to retrieve as a JSON string. For coverage, only 'SpendCoveredBySavingsPlans' is valid.
         group_by: Optional grouping of results as a JSON string. For coverage, supports SERVICE, REGION, or INSTANCE_FAMILY (NOT LINKED_ACCOUNT). Each entry is {"Type": ..., "Key": ...}; there is no "Value" field.
 
@@ -272,7 +272,13 @@ async def handle_aws_error(
         # Get AWS error details
         aws_error = error.response.get('Error', {})
         error_code = aws_error.get('Code', 'UnknownError')
-        aws_message = aws_error.get('Message') or 'No error message provided'
+        aws_message = aws_error.get('Message') or (
+            # Cost Explorer sends DataUnavailableException with an empty Message.
+            f'{service_name} has no data for this request '
+            '(DataUnavailableException; the service sent no message).'
+            if error_code == 'DataUnavailableException'
+            else 'No error message provided'
+        )
         request_id = error.response.get('ResponseMetadata', {}).get('RequestId', 'Unknown')
         http_status = error.response.get('ResponseMetadata', {}).get('HTTPStatusCode', 0)
 
 
@@ -18,7 +18,8 @@
 
 - ``retry_same_request``: the failure is transient (throttling, connection, 5xx).
 - ``modify_request``: the arguments must change before trying again.
-- ``do_not_retry``: the failure cannot be fixed during this run (permissions, opt-in).
+- ``do_not_retry``: the failure cannot be fixed during this run (permissions, opt-in, no data
+  for the request).
 
 The strategy is derived from the existing ``error_type`` values, which are left
 unchanged. Unknown or missing types get ``do_not_retry``.
@@ -49,6 +50,14 @@
     'The account is not opted in or enrolled for this feature. Do not retry; '
     'tell the user how to enable it.'
 )
+# Mapped by error_type, so it reaches every service that raises the code (Cost Explorer,
+# Pricing Calculator): keep it service-neutral. Tool descriptions carry the specifics.
+_HINT_DATA_UNAVAILABLE = (
+    'The service has no data for this request, so sending it again unchanged usually returns '
+    'the same error. Common causes are a time period too recent to have been processed yet, or '
+    'a filter value that matches nothing; the tool description may say when this happens. '
+    'Report that no data is available, not a failure and not a zero.'
+)
 
 # error_type -> (retry_strategy, hint). Covers both AWS error codes passed through by
 # handle_aws_error and the lowercase values set on local format_response errors.
@@ -101,7 +110,7 @@
     'OptInRequiredException': (DO_NOT_RETRY, _HINT_OPT_IN),
     'opt_in_required': (DO_NOT_RETRY, _HINT_OPT_IN),
     'enrollment_error': (DO_NOT_RETRY, _HINT_OPT_IN),
-    'DataUnavailableException': (DO_NOT_RETRY, None),
+    'DataUnavailableException': (DO_NOT_RETRY, _HINT_DATA_UNAVAILABLE),
 }
 
 # Families of AWS codes matched by prefix, checked after the exact table.
 
@@ -2105,3 +2105,19 @@ def test_description_documents_max_items_paging():
     assert 'next_token' in description
     for removed in ('max_pages', 'max_results', 'automatic pagination', 'Pagination is automatic'):
         assert removed not in description
+
+
+@pytest.mark.asyncio
+async def test_description_states_savings_plans_data_lag():
+    """The getSavingsPlansUtilization notes state the 2-3 day lag and the unmatched-filter case."""
+    tool = await cost_explorer_server.get_tool('cost-explorer')
+    assert tool is not None and tool.description
+    assert 'Data lags ~1 day' not in tool.description
+    assert 'set end_date to yesterday' not in tool.description
+    assert 'end_date must be before the current date' not in tool.description
+    assert 'report none/zero' not in tool.description
+    assert 'Data for the most recent 2-3 days (counting today) is not processed yet' in (
+        tool.description
+    )
+    assert 'an unknown SAVINGS_PLANS_TYPE matches nothing' in tool.description
+    assert 'report that no data is available for that window (not zero)' in tool.description
@@ -1355,3 +1355,13 @@ async def test_description_names_max_pages(self):
         description = tool.description or ''
         assert 'get_reservation_utilization takes max_pages (pages of 500 groups)' in description
         assert 'rounded up' not in description
+
+
+@pytest.mark.asyncio
+async def test_description_states_utilization_data_lag():
+    """Recent-day utilization windows return an empty-message DataUnavailableException."""
+    description = ' '.join((await _ri_description()).split())
+    assert 'utilization data for the most recent 2-3 days (counting today)' in description
+    assert 'which the service sends without a message' in description
+    assert 'not a failure and not zero utilization' in description
+    assert 'do not resend the identical request' in description
@@ -1577,6 +1577,28 @@ async def _description() -> str:
         assert tool is not None and tool.description
         return tool.description
 
+    async def test_states_the_data_lag_and_data_unavailable_causes(self):
+        """The lag is 2-3 days (excluding today is not enough), and unmatched filters fail too."""
+        description = ' '.join((await self._description()).split())
+        assert 'lags roughly one day' not in description
+        assert 'then the window resolves' not in description
+        assert 'most recent 2-3 days (counting today) is not processed yet' in description
+        assert 'excluding only today is not enough' in description
+        assert 'succeeds but silently leaves them out' in description
+        assert (
+            'A start_date at least 3 days before today is usually past that delay' in description
+        )
+        assert 'an unknown SAVINGS_PLANS_TYPE, for example, returns this error' in description
+        assert 'not zero utilization or coverage' in description
+
+    async def test_end_date_doc_states_the_data_lag(self):
+        """The end_date arg doc no longer says excluding today is enough."""
+        tool = await sp_performance_server.get_tool('sp-performance')
+        assert tool is not None
+        end_date_doc = tool.parameters['properties']['end_date'].get('description', '')
+        assert 'lags ~1 day' not in end_date_doc
+        assert 'last 2-3 days (counting today) is not processed yet' in end_date_doc
+
     async def test_lists_utilization_details_filter_dimensions(self):
         """Every GetSavingsPlansUtilizationDetails filter dimension is named."""
         description = await self._description()
 
@@ -332,6 +332,64 @@ async def test_handle_client_error_with_empty_message(self):
 
         assert result['message'] == 'No error message provided'
 
+    @pytest.mark.asyncio
+    async def test_data_unavailable_with_empty_message_says_no_data(self):
+        """Cost Explorer's empty-message DataUnavailableException is reported as no data."""
+        from awslabs.billing_cost_management_mcp_server.utilities.error_contract import (
+            add_retry_guidance,
+        )
+        from botocore.exceptions import ClientError
+
+        error = ClientError(
+            {
+                'Error': {'Code': 'DataUnavailableException', 'Message': ''},
+                'ResponseMetadata': {'HTTPStatusCode': 400},
+            },
+            'GetSavingsPlansUtilization',
+        )
+
+        result = add_retry_guidance(
+            await handle_aws_error(
+                AsyncMock(), error, 'get_savings_plans_utilization', 'Cost Explorer'
+            )
+        )
+
+        assert result['error_type'] == 'DataUnavailableException'
+        assert result['message'] == (
+            'Cost Explorer has no data for this request '
+            '(DataUnavailableException; the service sent no message).'
+        )
+        assert result['retry_strategy'] == 'do_not_retry'
+        assert 'The service has no data for this request' in result['hint']
+
+    @pytest.mark.asyncio
+    async def test_data_unavailable_without_message_key_says_no_data(self):
+        """A DataUnavailableException with no Message key at all is reported the same way."""
+        from botocore.exceptions import ClientError
+
+        error = ClientError({'Error': {'Code': 'DataUnavailableException'}}, 'GetCostForecast')
+
+        result = await handle_aws_error(AsyncMock(), error, 'getCostForecast', 'Cost Explorer')
+
+        assert result['message'] == (
+            'Cost Explorer has no data for this request '
+            '(DataUnavailableException; the service sent no message).'
+        )
+
+    @pytest.mark.asyncio
+    async def test_data_unavailable_keeps_a_service_message(self):
+        """A DataUnavailableException that carries a message passes it through unchanged."""
+        from botocore.exceptions import ClientError
+
+        error = ClientError(
+            {'Error': {'Code': 'DataUnavailableException', 'Message': 'No data yet.'}},
+            'GetCostAndUsage',
+        )
+
+        result = await handle_aws_error(AsyncMock(), error, 'getCostAndUsage', 'Cost Explorer')
+
+        assert result['message'] == 'No data yet.'
+
     @pytest.mark.asyncio
     async def test_handle_value_error(self):
         """Test handling ValueError."""
 
@@ -19,6 +19,8 @@
     format_response,
 )
 from awslabs.billing_cost_management_mcp_server.utilities.error_contract import (
+    _ERROR_TYPE_GUIDANCE,
+    _ERROR_TYPE_PREFIX_GUIDANCE,
     DO_NOT_RETRY,
     MODIFY_REQUEST,
     RETRY_SAME_REQUEST,
@@ -107,6 +109,33 @@ def test_account_state_is_not_retried(self, error_type):
         """Opt-in and data availability failures cannot be fixed during the run."""
         assert classify_error(error_type)[0] == DO_NOT_RETRY
 
+    def test_data_unavailable_hint_says_no_data_not_failure(self):
+        """DataUnavailableException tells the caller there is no data, and the usual causes."""
+        strategy, hint = classify_error('DataUnavailableException')
+        assert strategy == DO_NOT_RETRY
+        assert hint is not None
+        assert 'The service has no data for this request' in hint
+        assert 'too recent to have been processed yet' in hint
+        assert 'a filter value that matches nothing' in hint
+        assert 'not a failure and not a zero' in hint
+
+    def test_data_unavailable_hint_is_service_neutral(self):
+        """Pricing Calculator raises the same code, so the hint names no Cost Explorer report."""
+        hint = classify_error('DataUnavailableException')[1] or ''
+        for specific in ('Savings Plans', 'Reserved Instance', '2-3 days'):
+            assert specific not in hint
+
+    @pytest.mark.parametrize(
+        'error_type, guidance',
+        [*_ERROR_TYPE_GUIDANCE.items(), *_ERROR_TYPE_PREFIX_GUIDANCE],
+    )
+    def test_every_mapped_error_type_has_a_hint(self, error_type, guidance):
+        """A mapped error type always carries recovery guidance, not just a strategy.
+
+        Hints are keyed by error_type, so each must hold for every service that raises it.
+        """
+        assert guidance[1], f'{error_type} is mapped without a hint'
+
     @pytest.mark.parametrize(
         'error_type',
         [