diff --git a/x-pack/solutions/observability/plugins/observability_agent_builder/server/routes/ai_insights/apm_error/fetch_apm_error_context.ts b/x-pack/solutions/observability/plugins/observability_agent_builder/server/routes/ai_insights/apm_error/fetch_apm_error_context.ts
index d2a305d5adb37..d9092a8fc282d 100644
--- a/x-pack/solutions/observability/plugins/observability_agent_builder/server/routes/ai_insights/apm_error/fetch_apm_error_context.ts
+++ b/x-pack/solutions/observability/plugins/observability_agent_builder/server/routes/ai_insights/apm_error/fetch_apm_error_context.ts
@@ -161,7 +161,7 @@ export async function fetchApmErrorContext({
           },
           logger,
           categoryCount: 10,
-          terms: { 'trace.id': traceId },
+          fields: ['trace.id'],
         });
 
         return logCategories?.categories;
diff --git a/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/handler.ts b/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/handler.ts
index 2813a16f996e5..5f69ac60421c7 100644
--- a/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/handler.ts
+++ b/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/handler.ts
@@ -14,8 +14,7 @@ import type {
 import { getLogsIndices } from '../../utils/get_logs_indices';
 import { getTypedSearch } from '../../utils/get_typed_search';
 import { getTotalHits } from '../../utils/get_total_hits';
-import { getShouldMatchOrNotExistFilter } from '../../utils/get_should_match_or_not_exist_filter';
-import { timeRangeFilter } from '../../utils/dsl_filters';
+import { timeRangeFilter, kqlFilter } from '../../utils/dsl_filters';
 import { parseDatemath } from '../../utils/time';
 
 export async function getToolHandler({
@@ -25,7 +24,8 @@ export async function getToolHandler({
   index,
   start,
   end,
-  terms,
+  kqlFilter: kuery,
+  fields,
 }: {
   core: CoreSetup<
     ObservabilityAgentBuilderPluginStartDependencies,
@@ -36,15 +36,16 @@ export async function getToolHandler({
   index?: string;
   start: string;
   end: string;
-  terms?: Record<string, string>;
+  kqlFilter?: string;
+  fields: string[];
 }) {
   const logsIndices = index?.split(',') ?? (await getLogsIndices({ core, logger }));
   const boolFilters = [
     ...timeRangeFilter('@timestamp', {
-      ...getShouldMatchOrNotExistFilter(terms),
       start: parseDatemath(start),
       end: parseDatemath(end, { roundUp: true }),
     }),
+    ...kqlFilter(kuery),
     { exists: { field: 'message' } },
   ];
 
@@ -66,7 +67,7 @@ export async function getToolHandler({
       boolQuery: { filter: boolFilters, must_not: lowSeverityLogLevels },
       logger,
       categoryCount: 20,
-      terms,
+      fields,
     }),
     getFilteredLogCategories({
       esClient,
@@ -74,7 +75,7 @@ export async function getToolHandler({
       boolQuery: { filter: boolFilters, must: lowSeverityLogLevels },
       logger,
       categoryCount: 10,
-      terms,
+      fields,
     }),
   ]);
 
@@ -87,14 +88,14 @@ export async function getFilteredLogCategories({
   boolQuery,
   logger,
   categoryCount,
-  terms,
+  fields,
 }: {
   esClient: IScopedClusterClient;
   logsIndices: string[];
   boolQuery: QueryDslBoolQuery;
   logger: Logger;
   categoryCount: number;
-  terms: Record<string, string> | undefined;
+  fields: string[];
 }) {
   const search = getTypedSearch(esClient.asCurrentUser);
 
@@ -143,7 +144,7 @@ export async function getFilteredLogCategories({
                 top_hits: {
                   size: 1,
                   _source: false,
-                  fields: ['message', '@timestamp', ...Object.keys(terms ?? {})],
+                  fields: ['message', '@timestamp', ...fields],
                   sort: {
                     '@timestamp': { order: 'desc' },
                   },
diff --git a/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/tool.ts b/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/tool.ts
index cd4753f639c20..8002e8911b5aa 100644
--- a/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/tool.ts
+++ b/x-pack/solutions/observability/plugins/observability_agent_builder/server/tools/get_log_categories/tool.ts
@@ -18,6 +18,7 @@ import { timeRangeSchemaOptional, indexDescription } from '../../utils/tool_sche
 import { getAgentBuilderResourceAvailability } from '../../utils/get_agent_builder_resource_availability';
 import type { getFilteredLogCategories } from './handler';
 import { getToolHandler } from './handler';
+import { OBSERVABILITY_GET_CORRELATED_LOGS_TOOL_ID } from '../get_correlated_logs/tool';
 
 export interface GetLogCategoriesToolResult {
   type: ToolResultType.other;
@@ -37,11 +38,17 @@ export const OBSERVABILITY_GET_LOG_CATEGORIES_TOOL_ID = 'observability.get_log_c
 const getLogsSchema = z.object({
   ...timeRangeSchemaOptional(DEFAULT_TIME_RANGE),
   index: z.string().describe(indexDescription).optional(),
-  terms: z
-    .record(z.string(), z.string())
+  kqlFilter: z
+    .string()
     .optional()
     .describe(
-      'Optional field filters to narrow down results. Each key-value pair filters logs where the field exactly matches the value. Example: { "service.name": "payment", "host.name": "web-server-01" }. Multiple filters are combined with AND logic.'
+      'A KQL query to filter logs. Examples: service.name:"payment", host.name:"web-server-01", service.name:"payment" AND log.level:error'
+    ),
+  fields: z
+    .array(z.string())
+    .optional()
+    .describe(
+      'Additional fields to return for each log sample. "message" and "@timestamp" are always included. Example: ["service.name", "host.name"]'
     ),
 });
 
@@ -69,9 +76,15 @@ When to use:
 How it works:
 Groups similar log messages together using pattern recognition, returning representative categories with counts.
 
+After using this tool:
+- For high-count error categories, use \`${OBSERVABILITY_GET_CORRELATED_LOGS_TOOL_ID}\` to trace the sequence of events leading to those errors
+- Compare error patterns across services - the origin service often has different error types than affected downstream services (e.g., "constraint violation" vs "connection timeout")
+- Patterns like "timeout", "exhausted", "capacity", "limit reached" are often SYMPTOMS - look for what's causing the resource pressure
+- If you see resource lifecycle logs (acquire/release, open/close), check if counts match - mismatches can indicate leaks
+
 Do NOT use for:
-- Understanding the sequence of events for a specific error (use get_correlated_logs)
-- Investigating a specific incident in detail (use get_correlated_logs)
+- Understanding the sequence of events for a specific error (use ${OBSERVABILITY_GET_CORRELATED_LOGS_TOOL_ID})
+- Investigating a specific incident in detail (use ${OBSERVABILITY_GET_CORRELATED_LOGS_TOOL_ID})
 - Analyzing changes in log volume over time (use run_log_rate_analysis)`,
     schema: getLogsSchema,
     tags: ['observability', 'logs'],
@@ -86,7 +99,8 @@ Do NOT use for:
         index,
         start = DEFAULT_TIME_RANGE.start,
         end = DEFAULT_TIME_RANGE.end,
-        terms,
+        kqlFilter,
+        fields = [],
       } = toolParams;
 
       try {
@@ -97,7 +111,8 @@ Do NOT use for:
           index,
           start,
           end,
-          terms,
+          kqlFilter,
+          fields,
         });
 
         return {
diff --git a/x-pack/solutions/observability/test/api_integration_deployment_agnostic/apis/observability_agent_builder/tools/get_log_categories.spec.ts b/x-pack/solutions/observability/test/api_integration_deployment_agnostic/apis/observability_agent_builder/tools/get_log_categories.spec.ts
index e5f1db0dff745..7b4c427d9fdfd 100644
--- a/x-pack/solutions/observability/test/api_integration_deployment_agnostic/apis/observability_agent_builder/tools/get_log_categories.spec.ts
+++ b/x-pack/solutions/observability/test/api_integration_deployment_agnostic/apis/observability_agent_builder/tools/get_log_categories.spec.ts
@@ -10,7 +10,6 @@ import { timerange } from '@kbn/synthtrace-client';
 import { type LogsSynthtraceEsClient, generateLogCategoriesData } from '@kbn/synthtrace';
 import { OBSERVABILITY_GET_LOG_CATEGORIES_TOOL_ID } from '@kbn/observability-agent-builder-plugin/server/tools';
 import type { GetLogCategoriesToolResult } from '@kbn/observability-agent-builder-plugin/server/tools/get_log_categories/tool';
-import { first } from 'lodash';
 import type { DeploymentAgnosticFtrProviderContext } from '../../../ftr_provider_context';
 import { createAgentBuilderApiClient } from '../utils/agent_builder_client';
 
@@ -53,7 +52,7 @@ export default function ({ getService }: DeploymentAgnosticFtrProviderContext) {
         params: {
           start: START,
           end: END,
-          terms: { 'service.name': SERVICE_NAME },
+          kqlFilter: `service.name:"${SERVICE_NAME}"`,
         },
       });
 
@@ -81,7 +80,7 @@ export default function ({ getService }: DeploymentAgnosticFtrProviderContext) {
         params: {
           start: START,
           end: END,
-          terms: { 'service.name': SERVICE_NAME },
+          kqlFilter: `service.name:"${SERVICE_NAME}"`,
         },
       });
 
@@ -112,15 +111,13 @@ export default function ({ getService }: DeploymentAgnosticFtrProviderContext) {
         expect(category).to.have.property('count');
         expect(category.count).to.be.greaterThan(0);
 
-        // Sample should include requested fields
+        // Sample should include core fields
         expect(category.sample).to.have.property('message');
         expect(category.sample).to.have.property('@timestamp');
-        expect(category.sample).to.have.property('service.name');
-        expect(first(category.sample['service.name'])).to.be(SERVICE_NAME);
       });
     });
 
-    it('works without terms filter', async () => {
+    it('works without kqlFilter', async () => {
       const results = await agentBuilderApiClient.executeTool<GetLogCategoriesToolResult>({
         id: OBSERVABILITY_GET_LOG_CATEGORIES_TOOL_ID,
         params: {