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

      • Megamenu

        Finally! Megamenu's are now available in Zoho-Sites, after waiting for it and requesting it for years! BUT ... why am I asked to upgrade in order to use a megamenu? First: Zoho promised to always provide premium versions and options for all included Zoho-applications

      • Cancel and refund

        Hi, Yesterday I paid for the Zoho email subscription. Within a few minutes, I realized that the subscription counts one email ID as one user. To make another email ID for the same domain name, I'd have to pay for another user. I emailed right away to

      • One Contact with Multiple Accounts with Portal enabled

        I have a contact that manages different accounts, so he needs to see the invoices of all the companies he manage in Portal but I found it not possible.. any idea? I tried to set different customers with the same email contact with the portal enabled and

      • Kaizen# 209 - Answering Your Questions | All About Client Script

        Hello everyone! Welcome back to another exciting Kaizen post! Thanks for all your feedback and questions. In this post, let's see the answers to your questions related to Client Script. We took the time to discuss with our development team, carefully

      • To Do: shareable task links without login

        Hi! I’m using Zoho Mail and ToDo in my daily work, and I’ve run into one limitation that’s a real blocker for me. Right now, to share tasks with managers or directors, they need to have a Zoho account and be added to a group. In practice, many of them

      • Ability to turn off "Would you like this amount to be reflected in the Payment field?" message

        Team, Is there any way to turn off the message" Would you like this amount to be reflected in the Payment field?" when I make a payment? This is so annoying. This happens EVERY TIME I put an amount in the Payment Made field.

      • Unlock agreement intelligence with Zoho Sign's latest AI updates

        Hello! If you've been struggling with long, complex agreements and spending way too much time on them, here's exactly what you'll want to hear: Zoho Sign now integrates with OpenAI's ChatGPT to make agreement management smarter and simpler. Acting like

      • Currency abbreviations

        Hello, Im stuck, and need help. I need the currency fields for example, opportunity value, or total revenue, to be abbreviated, lets say for 1,000 - 1K, 1,000,000 - 1M, and so on, how should I do this?

      • Embed Sign Document

        Has anyone tried embedding a document in a webpage? I'm building a webpage (using PowerPage) and I'm trying to embed it using an iframe then I got this error: Refused to display 'https://sign.zoho.com/' in a frame because it set 'X-Frame-Options' to

      • We’re transitioning from Zoho ShowTime to TrainerCentral

        Hello everyone, Zoho ShowTime was originally built as a training platform to serve training agencies, HR teams, and individual trainers. As the platform grew, we realized that more creators and businesses could benefit from its capabilities. That’s why

      • Emails Are Not Being Delivered to My Inbox

        Hello Zoho Support Team, I am experiencing an issue with my Zoho Mail account. The most important problem is that emails are not being delivered to my inbox. Details: My Zoho Mail address: info@coreforcelife.com What happens: I am not receiving any incoming

      • Radar In Focus: Track customer support metrics using Radar's static reports

        Hello everyone, Welcome back to the Radar In Focus series, where we explore how Radar features can add value to your business. In this episode, we're looking at Radar static reports. The help desk is filled with vast amounts of data that can be analyzed

      • Mail ToDo & Tasks Webhooks

        Our company uses Zoho ToDo inside Mail to manage our tasks. When I create a task and assign it to a team member it does not notify them unless I add a reminder via mail. I'm trying to create a webhook for when a task is created to send a cliq message

      • Allocating inventory to specific SO's

        Is there a way that allocate inventory to a specific sales order? For example, let's say we have 90 items in stock. Customer 1 orders 100 items. This allocates all 90 items to their order, and they have a back order for the remaining 10 items which could

      • Improved UI for a Seamless User Experience - Calls, Tasks, and Meetings

        Hello all, We are making UI unification across CRM so that the UI experience is seamless across the product. As part of that effort, we have made changes to the details page of activity-based module records—Meetings, Calls, and Tasks. Let's look at these

      • Where can I find rejected inbound mails and their reason for rejection

        Hi, I was recently made aware by a mailing list which I am subscribed to (ffmpeg-devel@ffmpeg.org) that my Zoho mail Mail account is rejecting some emails. If I look under Admin Panel > Security & Compliance > Quarantine > Incoming, the list there is

      • Refund

        Hi There, Please refund me asap possible, because of no support given. Thank you

      • تغيير عمله الدفع"Change payment currency"

        ما هى طريقه تغيير عمله الدفع "ما هي طريقة تغيير عملة الدفع؟"

      • How do I fix this? Unable to send message; Reason:554 5.1.8 Email Outgoing Blocked.

        How do I fix this? Unable to send message; Reason:554 5.1.8 Email Outgoing Blocked.

      • Attention API Users: Upcoming Support for Renaming System Fields

        Hello all! We are excited to announce an upcoming enhancement in Zoho CRM: support for renaming system-defined fields! Current Behavior Currently, system-defined fields returned by the GET - Fields Metadata API have display_label and field_label properties

      • Zia's ability to generate and improve content extended to Desk mobile app (iOS and Android)

        In support, agents will have to understand customers' pain points completely to provide empathetic personalized solutions and a positive experience. However, at times, agents might find it challenging to comprehend the customer issues and connect with

      • BANK FEED - MAYBANK , provider from YODLEE IS NOT WORKING

        As per topic, the provider YODLEE is not working for the BANK FEED. It have been reported since 2023 Q3, and second report on 2023 Q4. now almost end of 2024 Q1, and coming to 2024 Q2. Malaysia Bank Maybank is NOT working. can anyone check on this issue?

      • Zoho Sign product updates - Q3 2025

        Hello everyone! Q3 was all about AI. Here's the list of features and enhancements that have gone live, along with a list of what we have in pipeline for the last quarter: AI-powered agreement management Sending documents and authenticating recipients

      • Zoho sites header

        Good day, Im stuck with this situation. I choose a template for my website creation. I have tweaked every instance of the visual editor, regarding the header, I have created created customize fonts presets... I have followed every single step. and my

      • Zoho Books Sandbox environment

        Hello. Is there a free sandbox environment for the developers using Zoho Books API? I am working on the Zoho Books add-on and currently not ready to buy a premium service - maybe later when my add-on will start to bring money. Right now I just need a

      • Quick Create needs Client Script support

        As per the title. We need client scripts to apply at a Quick Create level. We enforce logic on the form to ensure data quality, automate field values, etc. However, all this is lost when a user attempts a "Quick Create". It is disappointing because, from

      • Kaizen #152 - Client Script Support for the new Canvas Record Forms

        Hello everyone! Have you ever wanted to trigger actions on click of a canvas button, icon, or text mandatory forms in Create/Edit and Clone Pages? Have you ever wanted to control how elements behave on the new Canvas Record Forms? This can be achieved

      • DNS set up

        I want to create an email with my company domain. When I tried to add new record with cloudflare it didn't work. The DNS record can't be manually added. I followed the instruction but still can't add it. Could you help?

      • Pocket from Mozilla is closing shop. Don’t lose your favorites . Move them to Zoho Mail Bookmarks now! 📥🔖

        The end of Pocket shouldn't mean the end of your important links and content. Easily import them into Zoho Mail's Bookmarks and continue right where you left off. You can bring over your entire Saves, Collections, and tags just the way they are. Bookmarks

      • General suggestions

        Hello, I've picked this forum as it is at the top of the list! :) First suggestion: A general forum for issues and comments that are not specific to a particular Zoho application. Second suggestion: Put a link on the home page to "Zoho Identity Access Manager" The first suggestion came about because I didn't know where to post the second! ;) Regards Mark

      • Can't upload attachments.

        I can't upload attachment in Zoho Mail.

      • Need Guidance on SPF Flattening for Zoho Mail Configuration

        Hi everyone, I'm hoping to get some advice on optimizing my SPF record for a Zoho Mail setup. I use Zoho Mail along with several other Zoho services, and as a result, my current SPF record has grown to include multiple include mechanisms. My Cloudflare

      • How use

        Good morning sir I tried Zoho Mail

      • Zoho Mail Desktop App Not Loading + Can’t Manage Multiple Accounts

        Hi everyone, I’ve been having ongoing issues with the Zoho Mail desktop app for the past few weeks. The app starts to load but gives up midway and never actually opens — there’s no error message, it just stops loading. The main reason I use the desktop

      • Error when sending emails from Zoho

        Hello, When trying to send an email from Zoho CRM I keep getting the below error: javax.mail.AuthenticationFailedException: 535 5.7.139 Authentication unsuccessful, the user credentials were incorrect. Any support on this will be much appreciated. Thanks,

      • Zoho Tables is now live in Australia & New Zealand!

        Hey everyone! We’ve got some great news to share — Zoho Tables is now officially available in the Australian Data Center serving users across Australia and New Zealand regions! Yes, it took us a bit longer to get here, but this version of Zoho Tables

      • Not all emails from outlook365 migrated to my new zoho account

        I recently setup a new email address hosted by zoho. I migrated all my folders and email from my Outlook365 account to my new zoho account, but not all my emails migrated. Looks like only the past 12 months, or so, made the move. How do I get the rest

      • Clients not receiving emails

        I've been informed that my emails are not being received. Is there anything that I should look into to rectify this? Many thanks!

      • Max numbr of IMAP Accounts in Zoho Mail?

        In Zoho mail, you can manage the inboxes of other accounts using IMAP (and POP, actually) https://www.zoho.com/mail/help/external-imap-accounts.html Is there a max to the number of inboxes we can add?

      • Formula Fields Trouble

        Hi,  I can't get even a simple formula field to work and must be doing something dumb. This formula: If(Len(Trim(${Quotes.Subject}))=0,1,2) Gives the error: You used the wrong type of data in an argument. Check what you entered between the parentheses of your functions to make sure you put the right kind of data in the right place. This formula: Len(Trim(${Quotes.Subject}))=0 Gives the error: Syntax Error. Check the examples for any functions you're using to see if you formatted them correctly. Make

      • Next Page