diff --git a/packages/api/src/__tests__/assistant-tools-dashboard-detail.test.ts b/packages/api/src/__tests__/assistant-tools-dashboard-detail.test.ts
index db0a789..ef87d21 100644
--- a/packages/api/src/__tests__/assistant-tools-dashboard-detail.test.ts
+++ b/packages/api/src/__tests__/assistant-tools-dashboard-detail.test.ts
@@ -64,6 +64,7 @@ describe("assistant dashboard tools detail aggregation", () => {
           calendarContextCount: 1,
           resourceCount: 4,
           groupCount: 1,
+          baseAvailableHours: 416.2,
           calendarLocations: [
             {
               countryCode: "DE",
@@ -79,6 +80,10 @@ describe("assistant dashboard tools detail aggregation", () => {
           remainingCapacityHours: 79.8,
           overbookedHours: 0,
           utilizationPct: 80,
+          effectiveAvailableHours: 400.2,
+          publicHolidayHoursDeduction: 16,
+          absenceDayEquivalent: 1.5,
+          absenceHoursDeduction: 12.5,
         },
       },
     ]);
@@ -190,6 +195,19 @@ describe("assistant dashboard tools detail aggregation", () => {
               effectiveAvailableHours: 400.2,
             },
           ],
+          explainability: {
+            periodStart: "2026-03-01",
+            periodEnd: "2026-03-31",
+            resourceCount: 4,
+            groupCount: 1,
+            baseAvailableHours: 416.2,
+            effectiveAvailableHours: 400.2,
+            publicHolidayHoursDeduction: 16,
+            absenceDayEquivalent: 1.5,
+            absenceHoursDeduction: 12.5,
+            remainingCapacityHours: 79.8,
+            overbookedHours: 0,
+          },
         },
       ],
       topResources: [
diff --git a/packages/api/src/__tests__/dashboard-procedure-support.test.ts b/packages/api/src/__tests__/dashboard-procedure-support.test.ts
index 985d567..10695dc 100644
--- a/packages/api/src/__tests__/dashboard-procedure-support.test.ts
+++ b/packages/api/src/__tests__/dashboard-procedure-support.test.ts
@@ -167,8 +167,19 @@ describe("dashboard procedure support", () => {
         capacityHours: 200.12,
         utilizationPct: 80,
         derivation: {
+          periodStart: "2026-03-01",
+          periodEnd: "2026-03-31",
           calendarContextCount: 1,
+          resourceCount: 5,
+          groupCount: 2,
+          baseAvailableHours: 216,
+          effectiveAvailableHours: 200.12,
+          publicHolidayHoursDeduction: 8,
+          absenceDayEquivalent: 1,
+          absenceHoursDeduction: 7.88,
           calendarLocations: [{ countryCode: "DE", federalState: "BY", metroCityName: "Munich" }],
+          remainingCapacityHours: 39.78,
+          overbookedHours: 0,
         },
       },
     ]);
@@ -228,6 +239,19 @@ describe("dashboard procedure support", () => {
             utilizationPct: 80,
             calendarContextCount: 1,
             calendarLocations: [{ countryCode: "DE", federalState: "BY", metroCityName: "Munich" }],
+            explainability: {
+              periodStart: "2026-03-01",
+              periodEnd: "2026-03-31",
+              resourceCount: 5,
+              groupCount: 2,
+              baseAvailableHours: 216,
+              effectiveAvailableHours: 200.12,
+              publicHolidayHoursDeduction: 8,
+              absenceDayEquivalent: 1,
+              absenceHoursDeduction: 7.88,
+              remainingCapacityHours: 39.78,
+              overbookedHours: 0,
+            },
           },
         ],
         topResources: [
diff --git a/packages/api/src/__tests__/dashboard-router.test.ts b/packages/api/src/__tests__/dashboard-router.test.ts
index 9c96a05..5aeb215 100644
--- a/packages/api/src/__tests__/dashboard-router.test.ts
+++ b/packages/api/src/__tests__/dashboard-router.test.ts
@@ -757,6 +757,33 @@ describe("dashboard router", () => {
           totalHours: 320.4,
           capacityHours: 400.2,
           utilizationPct: 80,
+          derivation: {
+            periodStart: "2026-03-01",
+            periodEnd: "2026-03-31",
+            calendarContextCount: 1,
+            resourceCount: 4,
+            groupCount: 1,
+            baseAvailableHours: 416.2,
+            effectiveAvailableHours: 400.2,
+            publicHolidayHoursDeduction: 16,
+            absenceDayEquivalent: 1.5,
+            absenceHoursDeduction: 12.5,
+            calendarLocations: [
+              {
+                countryCode: "DE",
+                countryName: "Germany",
+                federalState: "BY",
+                metroCityName: "Augsburg",
+                resourceCount: 4,
+                effectiveAvailableHours: 400.2,
+              },
+            ],
+            bookedHours: 320.4,
+            capacityHours: 400.2,
+            remainingCapacityHours: 79.8,
+            overbookedHours: 0,
+            utilizationPct: 80,
+          },
         },
       ]);
       vi.mocked(getDashboardTopValueResources).mockResolvedValue([
@@ -823,8 +850,30 @@ describe("dashboard router", () => {
             totalHoursPerDay: 320.4,
             capacityHours: 400.2,
             utilizationPct: 80,
-            calendarContextCount: 0,
-            calendarLocations: [],
+            calendarContextCount: 1,
+            calendarLocations: [
+              {
+                countryCode: "DE",
+                countryName: "Germany",
+                federalState: "BY",
+                metroCityName: "Augsburg",
+                resourceCount: 4,
+                effectiveAvailableHours: 400.2,
+              },
+            ],
+            explainability: {
+              periodStart: "2026-03-01",
+              periodEnd: "2026-03-31",
+              resourceCount: 4,
+              groupCount: 1,
+              baseAvailableHours: 416.2,
+              effectiveAvailableHours: 400.2,
+              publicHolidayHoursDeduction: 16,
+              absenceDayEquivalent: 1.5,
+              absenceHoursDeduction: 12.5,
+              remainingCapacityHours: 79.8,
+              overbookedHours: 0,
+            },
           },
         ],
         topResources: [
diff --git a/packages/api/src/router/dashboard-procedure-support.ts b/packages/api/src/router/dashboard-procedure-support.ts
index e5576c8..858ae50 100644
--- a/packages/api/src/router/dashboard-procedure-support.ts
+++ b/packages/api/src/router/dashboard-procedure-support.ts
@@ -242,6 +242,21 @@ export async function getDashboardDetail(ctx: DashboardProcedureContext, input:
         utilizationPct: entry.utilizationPct ?? null,
         calendarContextCount: entry.derivation?.calendarContextCount ?? 0,
         calendarLocations: entry.derivation?.calendarLocations ?? [],
+        explainability: entry.derivation
+          ? {
+              periodStart: entry.derivation.periodStart,
+              periodEnd: entry.derivation.periodEnd,
+              resourceCount: entry.derivation.resourceCount,
+              groupCount: entry.derivation.groupCount,
+              baseAvailableHours: entry.derivation.baseAvailableHours,
+              effectiveAvailableHours: entry.derivation.effectiveAvailableHours,
+              publicHolidayHoursDeduction: entry.derivation.publicHolidayHoursDeduction,
+              absenceDayEquivalent: entry.derivation.absenceDayEquivalent,
+              absenceHoursDeduction: entry.derivation.absenceHoursDeduction,
+              remainingCapacityHours: entry.derivation.remainingCapacityHours,
+              overbookedHours: entry.derivation.overbookedHours,
+            }
+          : null,
       }));
   }