diff --git a/.lycheeignore b/.lycheeignore
index 1b6a61169..4c14ce320 100644
--- a/.lycheeignore
+++ b/.lycheeignore
@@ -1,3 +1,4 @@
 https://localhost:*
 http://localhost:*
 http://webhook:8080
+https://api.openai.com/v1/chat/completions
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 94d891a4b..213de17b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Added `_type` to `termvector` and `mtermvector` ([#734](https://github.com/opensearch-project/opensearch-api-specification/pull/734))
 - Added missing `cancelled` and `resource_stats` to `/_reindex/{task_id}/_rethrottle` ([#740](https://github.com/opensearch-project/opensearch-api-specification/pull/740))
 - Added missing `cancellation_time_millis` to `POST /_tasks/_cancel` ([#747](https://github.com/opensearch-project/opensearch-api-specification/pull/747))
+- Added support for combining output variables ([#737](https://github.com/opensearch-project/opensearch-api-specification/pull/737))
 - Added 404 response to `/_search/scroll` ([#749](https://github.com/opensearch-project/opensearch-api-specification/pull/749))
 - Added `node_failures` to `DELETE /_search/scroll` and `DELETE /_search/scroll/{scroll_id}` ([#749](https://github.com/opensearch-project/opensearch-api-specification/pull/749))
 
diff --git a/TESTING_GUIDE.md b/TESTING_GUIDE.md
index 2812b37b2..c4590bd0a 100644
--- a/TESTING_GUIDE.md
+++ b/TESTING_GUIDE.md
@@ -244,7 +244,9 @@ Consider the following chapters in [ml/model_groups](tests/plugins/ml/ml/model_g
 ```
 As you can see, the `output` field in the first chapter saves the `model_group_id` from the response body. This value is then used in the subsequent chapters to query and delete the model group.
 
-You can also supply defaults for output values, e.g. for `payload._version` used in [cluster/routing/awareness/weights.yaml](tests/routing/cluster/routing/awareness/weights.yaml).
+You can combine multiple values, e.g. `task_id: ${task.node}:${task.id}`.
+
+You can supply defaults for output values, e.g. for `payload._version` used in [cluster/routing/awareness/weights.yaml](tests/routing/cluster/routing/awareness/weights.yaml).
 
 ```
 version:
diff --git a/tests/plugins/ml/ml/connectors.yaml b/tests/plugins/ml/ml/connectors.yaml
index 201019c04..c19939634 100644
--- a/tests/plugins/ml/ml/connectors.yaml
+++ b/tests/plugins/ml/ml/connectors.yaml
@@ -33,10 +33,10 @@ chapters:
         actions:
           - action_type: predict
             method: POST
-            url: 'https://${parameters.endpoint}/v1/chat/completions'
+            url: https://api.openai.com/v1/chat/completions
             headers:
-              Authorization: 'Bearer ${credential.openAI_key}'
-            request_body: '{ "model": "${parameters.model}", "messages": ${parameters.messages} }'
+              Authorization: Bearer Key
+            request_body: '{ "model": "model", "messages": "messages" }'
     response:
       status: 200
     output:
diff --git a/tools/src/helpers.ts b/tools/src/helpers.ts
index 4144afd31..d338f7960 100644
--- a/tools/src/helpers.ts
+++ b/tools/src/helpers.ts
@@ -160,3 +160,21 @@ export function write_json (file_path: string, content: any, replacer?: (this: a
 export async function sleep (ms: number): Promise<void> {
   await new Promise<void>((resolve) => setTimeout(resolve, ms))
 }
+
+/**
+ * Returns a string split using a delimiter, but only up to a certain number of times,
+ * returning the remainder of the string as the last element if the result.
+ *
+ * @param str a string
+ * @param delim delimiter
+ * @param count max number of splits
+ * @returns an array of strings
+ */
+export function split(str: any, delim: string, count: number = 0): string[] {
+  if (str === undefined) return []
+  const parts = str.split(delim)
+  if (count <= 0 || parts.length <= count) return parts
+  const result = parts.slice(0, count - 1)
+  result.push(parts.slice(count - 1).join(delim))
+  return result
+}
diff --git a/tools/src/tester/OutputReference.ts b/tools/src/tester/OutputReference.ts
new file mode 100644
index 000000000..a76fb6249
--- /dev/null
+++ b/tools/src/tester/OutputReference.ts
@@ -0,0 +1,57 @@
+/*
+* Copyright OpenSearch Contributors
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+import { split } from "../helpers"
+
+export class OutputReference {
+  chapter_id: string
+  output_name: string
+
+  constructor(chapter_id: string, output_name: string) {
+    this.chapter_id = chapter_id
+    this.output_name = output_name
+  }
+
+  /**
+   * Parses a string and returns a collection of output references that it may contain.
+   *
+   * @param str a string
+   * @returns an array of output references
+   */
+  static parse(str: string): OutputReference[] {
+    const pattern = /\$\{([^}]+)\}/g
+    let match
+    var result = []
+    while ((match = pattern.exec(str)) !== null) {
+      const spl = split(match[1], '.', 2)
+      result.push(new OutputReference(spl[0], spl[1]))
+    }
+    return result
+  }
+
+  /**
+   * Replaces occurrences of output references.
+   * Takes special care of preserving the type of the reference value if the entire string is a reference.
+   *
+   * @param str a string that may contain output references
+   * @param callback a callback for fetching reference values
+   * @returns a string with output references replaced by their values
+   */
+  static replace(str: string, callback: (chapter_id: any, variable: any) => string): any {
+    let full_match = str.match(/^\$\{([^}]+)\}$/)
+    if (full_match) {
+      // the entire string is a reference, preserve the type of the returned value
+      const spl = split(full_match[1], '.', 2)
+      return callback(spl[0], spl[1])
+    } else return str.replace(/\$\{([^}]+)\}/g, (_, k) => {
+      const spl = split(k, '.', 2)
+      return callback(spl[0], spl[1])
+    })
+  }
+}
diff --git a/tools/src/tester/StoryEvaluator.ts b/tools/src/tester/StoryEvaluator.ts
index a17df942f..eb0bbf2f7 100644
--- a/tools/src/tester/StoryEvaluator.ts
+++ b/tools/src/tester/StoryEvaluator.ts
@@ -8,7 +8,7 @@
 */
 
 import { ChapterRequest, Parameter, SupplementalChapter } from './types/story.types'
-import { type StoryFile, type ChapterEvaluation, Result, type StoryEvaluation, OutputReference } from './types/eval.types'
+import { type StoryFile, type ChapterEvaluation, Result, type StoryEvaluation } from './types/eval.types'
 import type ChapterEvaluator from './ChapterEvaluator'
 import { overall_result } from './helpers'
 import { StoryOutputs } from './StoryOutputs'
@@ -17,6 +17,7 @@ import { ChapterOutput } from './ChapterOutput'
 import * as semver from '../_utils/semver'
 import _ from 'lodash'
 import { ParsedChapter, ParsedStory } from './types/parsed_story.types'
+import { OutputReference } from './OutputReference'
 
 export default class StoryEvaluator {
   private readonly _chapter_evaluator: ChapterEvaluator
@@ -217,10 +218,7 @@ export default class StoryEvaluator {
   static #extract_params_variables(parameters: Record<string, Parameter>, variables: Set<OutputReference>): void {
     Object.values(parameters ?? {}).forEach((param) => {
       if (typeof param === 'string') {
-        const ref = OutputReference.parse(param)
-        if (ref) {
-          variables.add(ref)
-        }
+        OutputReference.parse(param).forEach((ref) => variables.add(ref))
       }
     })
   }
@@ -229,10 +227,7 @@ export default class StoryEvaluator {
     const request_type = typeof request
     switch (request_type) {
       case 'string': {
-        const ref = OutputReference.parse(request as string)
-        if (ref !== undefined) {
-          variables.add(ref)
-        }
+        OutputReference.parse(request as string).forEach((ref) => variables.add(ref))
         break
       }
       case 'object': {
diff --git a/tools/src/tester/StoryOutputs.ts b/tools/src/tester/StoryOutputs.ts
index 41b8d9e71..b535bc62e 100644
--- a/tools/src/tester/StoryOutputs.ts
+++ b/tools/src/tester/StoryOutputs.ts
@@ -8,7 +8,7 @@
 */
 
 import { ChapterOutput } from './ChapterOutput'
-import { OutputReference } from './types/eval.types'
+import { OutputReference } from './OutputReference'
 import { type Parameter } from './types/story.types'
 
 export class StoryOutputs {
@@ -48,12 +48,9 @@ export class StoryOutputs {
   }
 
   resolve_string (str: string): any {
-    const ref = OutputReference.parse(str)
-    if (ref) {
-      return this.get_output_value(ref.chapter_id, ref.output_name)
-    } else {
-      return str
-    }
+    return OutputReference.replace(str, (chapter_id, output_name) => {
+      return this.get_output_value(chapter_id as string, output_name as string)
+    })
   }
 
   resolve_value (payload: any): any {
diff --git a/tools/src/tester/types/eval.types.ts b/tools/src/tester/types/eval.types.ts
index e65b80c3c..0686a6896 100644
--- a/tools/src/tester/types/eval.types.ts
+++ b/tools/src/tester/types/eval.types.ts
@@ -83,20 +83,3 @@ export enum Result {
   SKIPPED = 'SKIPPED',
   ERROR = 'ERROR',
 }
-
-export class OutputReference {
-  chapter_id: string
-  output_name: string
-  private constructor (chapter_id: string, output_name: string) {
-    this.chapter_id = chapter_id
-    this.output_name = output_name
-  }
-
-  static parse (str: string): OutputReference | undefined {
-    if (str.startsWith('${') && str.endsWith('}')) {
-      const spl = str.slice(2, -1).split('.', 2)
-      return { chapter_id: spl[0], output_name: spl[1] }
-    }
-    return undefined
-  }
-}
diff --git a/tools/tests/helpers.test.ts b/tools/tests/helpers.test.ts
index f91dde573..3e1f15476 100644
--- a/tools/tests/helpers.test.ts
+++ b/tools/tests/helpers.test.ts
@@ -8,7 +8,7 @@
 */
 
 import _ from 'lodash'
-import { delete_matching_keys, find_refs, sort_array_by_keys, to_json, to_ndjson } from '../src/helpers'
+import { delete_matching_keys, find_refs, sort_array_by_keys, to_json, to_ndjson, split } from '../src/helpers'
 
 describe('helpers', () => {
   describe('sort_array_by_keys', () => {
@@ -195,4 +195,27 @@ describe('helpers', () => {
       })).toEqual(new Set(['#1', '#2', '#3', '#dup', '#/schemas/schema1', '#/schemas/schema2']))
     })
   })
+
+  describe('split', () => {
+    test('undefined', () => {
+      expect(split(undefined, '.')).toEqual([])
+    })
+
+    test('one element', () => {
+      expect(split('str', '.')).toEqual(['str'])
+      expect(split('str', '.', -1)).toEqual(['str'])
+      expect(split('str', '.', 0)).toEqual(['str'])
+      expect(split('str', '.', 10)).toEqual(['str'])
+    })
+
+    test('multiple elements', () => {
+      expect(split('x.y.z', '.')).toEqual(['x', 'y', 'z'])
+      expect(split('x.y.z', '.', -1)).toEqual(['x', 'y', 'z'])
+      expect(split('x.y.z', '.', 0)).toEqual(['x', 'y', 'z'])
+      expect(split('x.y.z', '.', 1)).toEqual(['x.y.z'])
+      expect(split('x.y.z', '.', 2)).toEqual(['x', 'y.z'])
+      expect(split('x.y.z', '.', 3)).toEqual(['x', 'y', 'z'])
+      expect(split('x.y.z', '.', 4)).toEqual(['x', 'y', 'z'])
+    })
+  })
 })
diff --git a/tools/tests/tester/OutputReference.test.ts b/tools/tests/tester/OutputReference.test.ts
new file mode 100644
index 000000000..76aa4a067
--- /dev/null
+++ b/tools/tests/tester/OutputReference.test.ts
@@ -0,0 +1,39 @@
+/*
+* Copyright OpenSearch Contributors
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+import { OutputReference } from "tester/OutputReference";
+
+describe('OutputReference', () => {
+  let f = (id: any, k: any): string => `[${id}:${k}]`
+
+  describe('parse', () => {
+    it('replaces', () => {
+      expect(OutputReference.parse('string')).toEqual([])
+      expect(OutputReference.parse('${k.v}')).toEqual([new OutputReference('k', 'v')])
+      expect(OutputReference.parse('${k.value}')).toEqual([new OutputReference('k', 'value')])
+      expect(OutputReference.parse('${k.v.m}')).toEqual([new OutputReference('k', 'v.m')])
+      expect(OutputReference.parse('A reference to ${k.v.m} and ${x.y}.')).toEqual([
+        new OutputReference('k', 'v.m'),
+        new OutputReference('x', 'y')
+      ])
+    })
+  })
+
+  describe('replace', () => {
+    it('replaces', () => {
+      expect(OutputReference.replace('string', f)).toEqual('string')
+      expect(OutputReference.replace('${k.v}', f)).toEqual('[k:v]')
+      expect(OutputReference.replace('${k.value}', f)).toEqual('[k:value]')
+      expect(OutputReference.replace('${k.v.m}', f)).toEqual('[k:v.m]')
+      expect(OutputReference.replace('A reference to ${k.v.m} and ${x} and ${x.y}.', f)).toEqual(
+        'A reference to [k:v.m] and [x:undefined] and [x:y].'
+      )
+    })
+  })
+});
diff --git a/tools/tests/tester/StoryOutputs.test.ts b/tools/tests/tester/StoryOutputs.test.ts
index 3017b7a66..9339a860b 100644
--- a/tools/tests/tester/StoryOutputs.test.ts
+++ b/tools/tests/tester/StoryOutputs.test.ts
@@ -19,7 +19,11 @@ const story_outputs = new StoryOutputs({
 
 test('resolve_string', () => {
   expect(story_outputs.resolve_string('${chapter_id.x}')).toEqual(1)
+  expect(story_outputs.resolve_string('${chapter_id.y}')).toEqual(2)
   expect(story_outputs.resolve_string('${invalid_id.x}')).toBeUndefined()
+  expect(story_outputs.resolve_string('${invalid_id.y}')).toBeUndefined()
+  expect(story_outputs.resolve_string('${chapter_id.x} and ${chapter_id.y}')).toEqual('1 and 2')
+  expect(story_outputs.resolve_string('${chapter_id.x} and ${chapter_id.y} and ${invalid.invalid}')).toEqual('1 and 2 and undefined')
   expect(story_outputs.resolve_string('some_str')).toEqual('some_str')
 })
 
@@ -55,13 +59,19 @@ test('resolve_params', () => {
     a: '${chapter_id.x}',
     b: '${chapter_id.y}',
     c: 3,
-    d: 'str'
+    d: 'str',
+    e: '${chapter_id.x}:${chapter_id.y}',
+    f: 'x=${chapter_id.x}',
+    g: '${chapter_id.y}=y'
   }
   expect(story_outputs.resolve_params(parameters)).toEqual({
     a: 1,
     b: 2,
     c: 3,
-    d: 'str'
+    d: 'str',
+    e: '1:2',
+    f: 'x=1',
+    g: '2=y'
   })
 })