Kaizen #189: Manipulating Multi-Module Lookup (MML) Field using Zoho CRM APIs

Kaizen #189: Manipulating Multi-Module Lookup (MML) Field using Zoho CRM APIs

Hello everyone!

Welcome back to another week of Kaizen.
In this post, we explore the Multi-Module Lookup (MML) field in the Appointments module of Zoho CRM. You learn what an MML field is, how it works, and how to use it with Zoho CRM APIs.



Table of Contents:

  • What is a Multi-Module Lookup (MML) Field in Zoho CRM?
  • Use Cases for MML
  • How  the "Appointment For" (MML) field in the "Appointments" module works?
  • Creating a Record in the Appointments Module Using the Insert Records API
  • Retrieving a Record from the Appointments Module Using the Get Records API
  • Multi-module Lookup Using the COQL API
  • Multi-module Lookup Using the Bulk Read API
  • Frequently Asked Questions

What is a Multi-Module Lookup (MML) Field in Zoho CRM?

A Multi-Module Lookup (MML) field in Zoho CRM allows you to create a one-to-one relationship between a record in one module and a record from one of multiple other modules. Unlike a normal lookup field, which references a single module, an MML field can dynamically reference records from multiple modules. 
Without the MML field, users must create multiple lookup fields for each module, which complicates the CRM layout and user experience.

Note:
  • The multi-module lookup (multi_module_lookup) data type was introduced in Zoho CRM API version 3.
  • Currently, the MML field is available as a system-defined field named Appointment For in the Appointments module. 
  • The Appointment For field supports lookups to both Contacts and custom modules.
  • You cannot create a custom MML field in Zoho CRM.


Data Model Representation

MML's Data Model Representation

Use Cases for MML


Zylker Healthcare is a multi-specialty hospital that uses Zoho CRM to maintain its appointment scheduling process. 

In this setup, Zylker maintains two key modules:
  • Contacts module - Stores records of physicians and surgeons, including attending physicians, specialists, and surgeons who diagnose and refer patients.
  • Patients module - A custom module used to maintain records of all patients.

To improve the appointment booking process, Zylker uses the "Appointment For" Multi-Module Lookup (MML) field in the Appointments module. This field lets Zylker manage an appointment with either a Physician/Surgeon or a Patient, eliminating the need for multiple lookup fields.

How  the "Appointment For" (MML) field in the "Appointments" module works?

  • When creating an appointment, the user selects the "Appointment For" field.
  • The field displays records based on the selected module, either the Contacts or  Patients. 
  • The user selects the appropriate record (Contact or Patients) for the appointment.
  • A related list is automatically created in the selected module (Contact or Patients) as the Open Activities / Closed Activities to display all appointments associated with that record.

Creating a Record in the Appointments module using the Insert Records API

Before creating a record in the Appointments module via the Insert Records API, make sure you know the API names of the system-defined mandatory fields. These fields are required to create an appointment successfully.

System-defined Mandatory Fields:
  • Appointment_For (MML field)
  • Service_Name
  • Appointment_Start_Time
  • Appointment_Name
  • Member
  • Location

The below image shows how these system-defined mandatory fields appear in the Appointments module UI:

System-defined mandatory keys in the Appointments Module in UI view.

API calls you have to make before creating a record:

Before inserting a record into the Appointments module, it is important to know the API names of the fields and their parent modules. 

i. Use the GET - Module Metadata API to know the API name of the module. In our case, the Appointments module.

Request URL : {api-domain}/crm/v8/settings/modules
Request Method : GET

Sample Response :

 
In the API response, search for the module with "module_name": "Appointments" and check the value of the "api_name" key to get the API name of the module. This is the name you will use in all related API calls.

ii. Use the GET - Fields Metadata API and get fields metadata for the Appointments module. Here, you can find the API names of the mandatory fields along with other fields present in the Appointments module. 

Below is the API call & response for the multi-module lookup field along with other mandatory fields.

Request URL : {api-domain}/crm/v8/settings/fields?module=Appointments__s
Request Method : GET

Sample Response :


Note: The above image highlights only the key properties of the Multi-Module Lookup (MML) field from the field metadata response. The complete API response contains additional properties not shown here.

In the response:
  • The multi-module lookup field is identified by the key "data_type" with the value "multi_module_lookup".
  • The associated modules supported by the MML field (e.g., Contacts, Patients) are listed under the "modules" key.
  • Other mandatory fields like Service Name, Appointment Name, and Appointment Start Time can be identified by "system_mandatory": true.
The keys of the above multi_module_lookup JSON object are explained below:


"multi_module_lookup": {
    "display_label": "Appointments", // Display label of the module where the MML field is used
    "api_name": "Appointments__s", // API name of the Appointments module
    "modules": [ //List of modules associated with the Appointments module. 
        {
            "api_name": "Contacts", //API name of the associated module 
            "module_name": "Contacts", // Display Name of the module 
            "id": "5725767000000002179" //Unique ID of the module
        },
        {
            "api_name": "Patients", //API name of the associated custom module
            "module_name": "Patients", //Display label of the module
            "id": "5725767000006473007" //Unique module ID
        }
    }
]
},

Note: 
  • You cannot add or remove modules from the Multi-Module Lookup (MML) field using APIs. These actions are only available through the Zoho CRM UI.
  • Once a module is disassociated from the MML field, existing records associated with that module will remain in the Appointments module, and you will no longer be able to associate newly created records from the disassociated module using the MML field. 
The remaining system-defined mandatory fields, along with their API names, are listed below.

 

 System-defined Mandatory Field Names

 

 

System-defined Mandatory Field API Names

Service Name

Service_Name

Appointment Start Time

Appointment_Start_Time

Appointment Name

Appointment_Name

Member

Owner

Location

Location


Note: The system-defined mandatory fields can be identified by "system_mandatory": true.

Search the system-defined mandatory field names and get their API names.
With the field API names, use the following request and sample input body to create a record in the Appointments module using the Insert Records API.

Request URL : {{api-domain}}/crm/v8/Appointments__s
Request Method : POST

Request Body :

{
    "data": [
        {
            "Appointment_Name": "General Consultation",
            "Owner": {
                "name": "Patricia Boyle",
                "id": "5725767000000411001",
                "email": "patricia@zohotest.com"
            },
            "Appointment_Start_Time": "2025-04-15T13:00:00-07:00",
            "Appointment_End_Time": "2025-04-15T13:30:00-07:00",
            "Appointment_For": {
                "module": {
                    "api_name": "Contacts",
                    "id": "5725767000000002179"
                },
                "name": "John Doe",
                "id": "5725767000005607020"
            },
            "Service_Name": {
                "name": "General Check-up",
                "id": "5725767000006387029"
            },
            "Location": "Business Address"
        }
    ]
}


Sample Response:


{
    "data": [
        {
            "code": "SUCCESS",
            "details": {
                "Modified_Time": "2025-05-06T20:33:42-07:00",
                "Modified_By": {
                    "name": "Patricia Boyle",
                    "id": "5725767000000411001"
                },
                "Created_Time": "2025-05-06T20:33:42-07:00",
                "id": "5725767000006390001", //Unique ID if the newly created record. Please note that this record ID will be used in the following API get and update operations.
                "Created_By": {
                    "name": "Patricia Boyle",
                    "id": "5725767000000411001"
                }
            },
            "message": "record added",
            "status": "success"
        }
    ]
}



Note:
Only Contacts and custom modules are supported in the Multi-Module Lookup field. If you try to associate a new record with a module that has been removed from the MML field or an unsupported module in the MML field, the following error will be thrown. 


Retrieving a Record from the Appointments Module Using the Get Records API

Request URL : {{api-domain}}/crm/v8/Appointments__s/5725767000006390001
Request Method: GET

Request Response:

{
    "data": [
        {
            "Owner": {
                "name": "Patricia Boyle",
                "id": "5725767000000411001",
                "email": "patricia@zoho.com"
            },
            "$currency_symbol": "$",
            "Address": null,
            "Appointment_Start_Time": "2025-04-15T13:00:00-07:00",
            "Cancellation_Reason": null,
            "$field_states": null,
            "Appointment_For": {
                "module": {
                    "api_name": "Contacts",
                    "id": "5725767000000002179"
                },
                "name": "John Doe",
                "id": "5725767000005607020"
            },
            "Rescheduled_To": null,
            "$sharing_permission": "full_access",
            "Reschedule_Reason": null,
            "Additional_Information": null,
            "Last_Activity_Time": null,
            "Cancelled_Time": null,
            "Cancellation_Note": null,
            "Modified_By": {
                "name": "Patricia Boyle",
                "id": "5725767000000411001",
                "email": "patricia@zoho.com"
            },
            "Reschedule_Count": 0,
            "Rescheduled_By": null,
            "id": "5725767000006390001",
            "Rescheduled_Time": null,
            "Remind_At": null,
            "Appointment_End_Time": "2025-04-15T13:30:00-07:00",
            "Status": "Overdue",
            "Modified_Time": "2025-05-06T20:04:38-07:00",
            "Service_Name": {
                "name": "General Check-up",
                "id": "5725767000006387029"
            },
            "Created_Time": "2025-05-06T20:04:38-07:00",
            "testing": null,
            "Rescheduled_From": null,
            "Cancelled_By": null,
            "$editable": true,
            "Appointment_Name": "General Consultation",
            "Duration": 30,
            "Record_Status__s": "Available",
            "Created_By": {
                "name": "Patricia Boyle",
                "id": "5725767000000411001",
                "email": "patricia@zoho.com"
            },
            "Tag": [],
            "Location": "Business Address",
            "Reschedule_Note": null
        }
    ]
}


Updating MML Field Value Using the Update Records API

Request URL : {{api-domain}}/crm/v8/Appointments__s/5725767000006390001
Request Method: PUT

Request Body:

{
    "data": [
        {
            "Appointment_Start_Time": "2025-04-16T14:00:00-07:00", //Updating the Appointment_Start_Time
            "Appointment_End_Time": "2025-04-16T14:30:00-07:00", //Updating the Appointment_End_Time
            "Appointment_For": {
                "module": {
                    "api_name": "Employees", //Updating a different module
                    "id": "5725767000002161028"
                },
                "name": "Patrica", //A record from the Employees module
                "id": "5725767000006272001" //unique ID of the record
            }
        }
    ]
}


Multi-module Lookup Using the COQL API

Querying Inner Fields of Linked Modules within the MML Field

With the COQL API, you can query inner fields of linked modules within a Multi-Module Lookup (MML) field. This provides deeper insights into related fields data in a module. This query support is available from Zoho CRM API Version 7.

Sample Query:


{
 "select_query": "select 'Appointment_For->Contacts.Lead_Source' from Appointments__s where id is not null"
}

The above query retrieves the Lead Source field from the Contacts module within the Appointment_For MML field. 


Sample Response:



Querying Multi-Module Lookup Module Name

Querying the module name associated with each record in a Multi-Module Lookup (MML) field. This query support is available from Zoho CRM API Version 7.

Sample Query:

{
"select_query": "select Appointment_For.module.api_name, Appointment_For from Appointments__s where id is not null"
}


The Appointment_For.module.api_name returns the module name (e.g., Contacts or Accounts) for each record linked in the Appointment_For MML field.

Sample Response:


Multi-module Lookup Using the Bulk Read API

Bulk Read API allows you to fetch a large set of data i.e., you can fetch a maximum of 2,00,000 records in a single API call. 
Specify the API name of the Appointments module in the module JSON object when making API calls. Refer to the following section for an example.

Request Method : POST

Request Body :

{
    "callback": {
        "method": "post"
    },
    "query": {
        "module": {
            "api_name": "Appointments__s" //API name of the Appointments module
        },
        "file_type": "csv"
    }
}


Note: The Appointment_For field cannot be used in the criteria.

As the API is an asynchronous API, the response will not be available instantly; the bulk read job is scheduled, and the status can be checked. Once the job is completed, you will be notified in the callback URL. The records are available in a downloadable CSV file or ICS file (for events). See the Bulk Read API document to know how to view the status of the scheduled job and download the file, along with more sample requests and responses.

Sample Exported Response 



Frequently Asked Questions

1. Which modules are currently supported in the MML field?

Only Contacts and custom modules can be associated with an MML field.

2. What error is thrown if I try to associate a record with a removed or unsupported module in the MML field?

If you try to associate a record with a removed or unsupported module in an MML field, the system will throw an "INVALID_DATA" error.

3. Is the MML field available for all modules?

No, as of Zoho CRM API Version 8, the MML field is available only as a system-defined field in the Appointments module.

4. How do I get the list of modules associated with an MML field?

You can use the GET - Fields Metadata API for the Appointments module and look for the field with "data_type" : "multi_module_lookup" and check its "modules" JSON array.

5. Can I add or remove modules from a Multi-Module Lookup (MML) field via API?

Adding or removing modules in an MML field is not supported via API. These actions can only be done through the Zoho CRM UI.

6. What happens if I remove a module from an MML field?

If a module is removed from the MML through Zoho CRM UI, it can no longer be associated with new records, but existing records linked to that module will remain unaffected.

7. Is MML field supported in the Bulk Write API?

As of Zoho CRM API Version 8, the MML field is available only in the Appointments module as a system-defined field. The Appointments module is not supported in the Bulk Write API.

8. Is MML field supported in the Search API?

The MML field is not currently supported in the Search API.



We trust that this post meets your needs and is helpful. Let us know your thoughts in the comment section or reach out to us at support@zohocrm.com

Stay tuned for more insights in our upcoming Kaizen posts!

Cheers!!!


Related Readings:


      • Recent Topics

      • [Webinar] The Transformative Power of Gen BI

        Traditional decision-making tools are no longer enough. The integration of generative AI into business intelligence (BI) is proving to be a true game changer—enabling businesses to make faster, smarter, and better informed decisions. Early adopters of

      • Backorder process review - Automating Removal of Sales Order from "On Hold" When PO is Received

        Hello Zoho Inventory Team, Currently, sales orders in On Hold status are released only when the bill for the purchase order is created. In our workflow, it would be much more efficient if the sales order could automatically move out of On Hold as soon

      • How to access the saved Query using API?

        I have created a query in setting. Is it possible to access it from a API? What's the endpoint? I tried /v8/queries/important_deals but didnt' work.

      • création d'une base de données

        base de donnee d'un lycée

      • User Session variables to recall after form submit & redirect to menu

        Hey, Forgive me if this is a simple answer I have overlooked. I have built a big onboarding process for my SAAS platform which is built and managed by an external Dev team. I am hoping to embed my new creator app on the SAAS platform. I have a menu page

      • Zoho Writer Merge Template with data from Zoho Analytics Views

        Hello, Is there any way to pull information from Zoho Analytics and put it into a Merge Template? I am trying to create a bulk export of one report that filters on a field to create a single document for each of the filter fields.

      • Having to enter bill before stock shows as available.

        Hi, Am I right in thinking you must create a bill from the purchase order receipt before the goods are available for shipping?

      • Agent Availability Report

        From data to decisions: A deep dive into ticketing system reports Businesses need to track when their support agents check in and check out from work. This report, titled Agent Availability, is one of the static reports that helps managers track the number

      • AI-driven construction analytics using Zoho Projects Plus

        Construction projects thrive on timelines; if a project is completed on or before the expected time, it makes headlines, but if it gets delayed, the company’s credibility will be at risk. Such projects require precise planning and constant monitoring,

      • Canadian payroll

        Hello ZOHO, is any updates on when payroll for Canada will be available?

      • Unified customer view: Bringing product intelligence into your CRM data

        For businesses today, applications and digital interfaces are the main touch points in the customer journey. While Zoho CRM data already tells who your customers are and what they buy, Zoho Apptics tells you how they interact and engage with your product.

      • Zoho Creator SaaS app with multiple client AND multiple users

        I am close to finalizing a Zoho Creator app that will be used by different companies to manage sale info, and each company can have multiple users using the app. Things were going perfectly until I tried a search on a report. I use a database field in each table to separate the data for each company, which works great. BUT when I do a search, I get to see ALL the data. This means that Company A could easily see the data from Companies B and C via the built-in search. Is there a way to set up the

      • Project Change Orders and Additions

        We are in the process of migrating from QuickBooks Online to Zoho Books. We have Zoho One and like the ability to sync all of our data across everything. And I like that projects work in a way that's less dumb than QuickBooks. I'm trying to figure out

      • Track online, in-office, and client location meetings separately with the new meeting venue option

        Hello everyone! We’re excited to announce meeting enhancements in Zoho CRM that bring more clarity and structure to how meetings are categorized. You can now specify the meeting venue to clearly indicate whether a meeting is being held online, at the

      • Possible to send Zoom AI Companion transcripts and summaries to contacts in CRM?

        Title says it all. Is it possible to send Zoom AI Companion transcripts and summaries to contacts in Zoho CRM?

      • How do I edit the Calendar Invite notifications for Interviews in Recruit?

        I'm setting up the Zoho Recruit Interview Calendar system but there's some notifications I don't have any control over. I've turned off all Workflows and Automations related to the Calendar Scheduling and it seems that it's the notification that is sent

      • Posibility to add Emoticons on the Email Subject of Templates

        Hi I´ve tried to add Emoticons on the Subject line of Email templates, the emoticon image does show up before saving the template or if I add the Emoticon while sending an Individual email and placing it manually on the subject line. Emoticons also show

      • Clarity on extended contract status

        Clarity on “extended” status- How does Zoho “extend” a contract?  E.g. if client extends by 1 month, can the “end date” be adjusted accordingly in Zoho and tagged as “Extended” with a clear audit trail that also captures the client’s email? Note- Email

      • Customizing contract status

        Can we customize/add/remove status on Zoho contracts ourselves or does Zoho needs to do this? Context- There is a long list of status on Zoho but not all of them are relevant for us . There are few status which are missing and needs to be added. E.g-

      • Set Custom Business Calendars and Holidays for Global Teams

        Managing a project across diverse teams means accounting for more than just tasks and deadlines; it means acknowledging how and when each team actually works. Users might follow different working days or observe region-specific holidays that cannot be

      • [Integration edition] Deluge learning series - Integrations between Zoho apps and Third-party services with Deluge | 28 August 2025

        We’re excited to welcome you to the Deluge learning series: Integration edition! The Integration edition will run for three months: Session 1 – Integrating Zoho Apps with Deluge using inbuilt integration tasks Session 2 – Integrating Zoho Apps with Deluge

      • Critical Vulnerability in all major password manager plugins - is Zoho Vault affected?

        Hi Zoho, a security researcher found a critical clickjacking vulnerability in all major browser password managers: DOM-based Extension Clickjacking: Your Password Manager Data at Risk | Marek Tóth Is Zoho Vault affected as well? Apparently the Vault extension

      • Change eMail Template for Event-Invitations

        Hello ZOHO-CRM Team How I can change the eMail Template for Event-Invitations? I work with the German Version of the Free Version. I know how I can modify eMail alerts or Signature Templates, but where I can other eMails modify you send out? Thank you for your answer. Regards, Juerg

      • Need Your Insights

        Hi Zoho, I'm confused why the flow only sends to one output. setVariable15 is from a list. It doesn't consider the 2nd entry. Any thoughts?

      • Map Dependency Fields - How can can I limit picklist values from a multi-select Parent field?

        I know the "Map Dependency Fields" feature doesn't allow a multi-select parent field. However, I need the functionality. Can I do it through a deluge function, and would it still support color coding picklists? We need the color coding for quick scanning

      • DYK 1 - Color Palette for Enhanced Visual Identification of Status

        Introducing the Did You Know series of posts. The goal of this series is to familiarize users with certain features or enhancements in Zoho Projects that may not be evident at first glance. The first post in this series deals with color palettes for indicating

      • Invalid field in the COQL query

        Dear Zoho Support! I believe that you already helped me with a similar problem a few years ago. One of my clients has a custom field named "LOB" in the "Deals" Module (see the field's metadata below). The COQL query using this field: : "select id, Deal_Name,

      • Automating Employee Birthday Notifications in Zoho Cliq

        Have you ever missed a birthday and felt like the office Grinch? Fear not, the Cliq Developer Platform has got your back! With Zoho Cliq's Schedulers, you can be the office party-cipant who never forgets a single cake, balloon, or awkward rendition of

      • Transferring domain registration to new registrar and switching email hosting at the same time?

        I need to transfer an existing domain uv cure adhesive that's currently with SiteGround to Porkbun. I also need to move the existing custom email addresses from SiteGround to Zoho Mail. I'm not sure if I should transfer the domain first and then tackle

      • Split deposits

        Can Zoho do split deposits. One deposit, two checks for two separate invoices from different customers. This is one of the most common tasks I can imaging. When I mark the two invoices paid, there are two deposits in bank register. When I try to match,

      • Deactivate Desk Contact without Deleting Contat

        We have a client who has multiple tenants for regulatory purposes, and as such, has a few users that have email addresses in both tenants. They've then emailed into the ticketing system, so we have multiple contacts (no big deal, we want to keep their

      • [Free Webinar] Learning Table Series - Zoho Creator for Asset Management with AI Enhancements

        Hello Everyone! We’re excited to invite you to another edition of Learning Table Series, where we showcase how Zoho Creator empowers industries with innovative and automated solutions. Each month highlights a specific sector, and this time our focus is

      • Menu Building is completely broken

        I have been 3 hours, I have not been able to edit the menu. Either it is completely broken, very little intuitive or I do now know anything... There is no way to create a megamenu, no way to create a menu. Despite the fact I go to menu configurartion

      • Can you sell Subscriptions using Zoho Commerce?

        In addition to physical products and the apparently coming soon 'Digital Products', it is possible to sell Subscriptions using Zoho Commerce?

      • Kaizen #197: Frequently Asked Questions on GraphQL APIs

        🎊 Nearing 200th Kaizen Post – We want to hear from you! Do you have any questions, suggestions, or topics you would like us to cover in future posts? Your insights and suggestions help us shape future content and make this series better for everyone.

      • Multiple Languages for Product Names

        Hi, I use 2 languages: spanish and english. I want to have for every product a name in spanish and a name on english. I want to have to possibility of choosing one of these languages when making an invoice or a purchase order. Is there any way to do

      • Item with name in different languate

        Hello, is there a way to have an item with its name in different languages? For example: I sell an item in different markets and I'd like to have a Proposal and the Invoice with the Item Name in a specific language. Rino Bertolotto Zoho Specialist, STESA srl

      • Contacts with most tickets? Alarm for multiple tickets?

        Is it possible to see through the analytics/reports which contacts are creating the most tickets (not the most discussed ones)? Also, is there a way to set up a notification if a contact creates multiple tickets within a certain time frame?

      • Issue with Template Subject Line Format in Zoho CRM

        Hi Team, I’ve noticed that when I update the subject line of an email template in Zoho CRM, it sometimes appears in an incorrect format when used. Please see the attached screenshot for reference. Kindly look into this issue and fix this issue from backend

      • Two Data Labels in Bar Chart

        I need to create a bar chart that has both the SUM and COUNT. I've concatenated them into a formula but it converts it into a stacked bar / scattered chart. The bar chart is no longer accessible. Since i'm comparing YOY, it would be best to have it in

      • Next Page