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:


    • Sticky Posts

    • Kaizen #198: Using Client Script for Custom Validation in Blueprint

      Nearing 200th Kaizen Post – 1 More to the Big Two-Oh-Oh! 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.

    • Kaizen #226: Using ZRC in Client Script

      Hello everyone! Welcome to another week of Kaizen. In today's post, lets see what is ZRC (Zoho Request Client) and how we can use ZRC methods in Client Script to get inputs from a Salesperson and update the Lead status with a single button click. In this

    • Kaizen #222 - Client Script Support for Notes Related List

      Hello everyone! Welcome to another week of Kaizen. The final Kaizen post of the year 2025 is here! With the new Client Script support for the Notes Related List, you can validate, enrich, and manage notes across modules. In this post, we’ll explore how

    • Kaizen #217 - Actions APIs : Tasks

      Welcome to another week of Kaizen! In last week's post we discussed Email Notifications APIs which act as the link between your Workflow automations and you. We have discussed how Zylker Cloud Services uses Email Notifications API in their custom dashboard.

    • Kaizen #216 - Actions APIs : Email Notifications

      Welcome to another week of Kaizen! For the last three weeks, we have been discussing Zylker's workflows. We successfully updated a dormant workflow, built a new one from the ground up and more. But our work is not finished—these automated processes are

    • Recent Topics

    • Service currently unavailable

      Service currently unavailable It is not possible to access email; the entire Zohoworkplace platform is down

    • User Permission Log

      Our external auditors are asking for a way to view changes made to user permissions (basically, a user permission change log). Is this feature built into Creator? 

    • E-mail down

      We cannot get into our email inboxes, are you affected by a Microsoft update issue? How long do you think as to restoration?

    • ZOHO MAIL SERVICE NOT WORKING

      Hello i've a problem my zoho mail account says a display with this text "our service is temporally unavaible"

    • ايميل مجانى

      Can I create a free email account on Zahoo?

    • Sign up for email for a domain

      Hi - I thought I had signed up for a domain of <domain>.com, but only see the email of @zohomail.com . How do I get the <domain.com> domain linked to my email?

    • Feature Request: Include Creator-applicable Deluge updates in the Creator Release Notes

      I'd like to put forward a suggestion about how Deluge updates are surfaced to Zoho Creator developers, and I'm hoping the Creator team will consider it. Zoho Creator is built on Deluge. Every workflow, custom function, validation and schedule we write

    • Zoho Books | Product updates | June 2026

      Hello users, Welcome to this month's roundup of what's new in Zoho Books! We have an exciting line-up this time. The highlight is the launch of the all-new France Edition with full ISCA compliance. We're also introducing features such as Layout Rules

    • Partner with HDFC And Sbi Bank.

      Hdfc and sbi both are very popular bank if zoho books become partner with this banks then many of the zoho books users will benefit premium features of partnered banks.

    • name change of company in same GSTIN registration . how to retain historical company name for past transactions?

      hello I have recently change my company name from BHANU DIAM to BHANUMATI IMPEX in same GSTIN registration number While i have update the company name in profile name that change all my historic data like sale invoices and purchase bill , i would like

    • AUTOMATION OF INVOICE PROCESSING

      Dear Zoho Books Product Team, I hope this message finds you well. I’m reaching out as a dedicated Zoho Books user with a product idea that I genuinely believe could transform how businesses handle purchase invoicing — and set Zoho Books apart as the smartest

    • Zoho Books | Product updates | July 2026

      Hello users, We’re excited to bring you the latest updates in Zoho Books for July 2026! This month's release introduces Terminal Payments, CMP-08 filing for composition taxpayers, SEPA Credit Transfer support, the new Receipts and Payments Report for

    • Zoho ERP | Product updates | June 2026

      Hello users, We launched Zoho ERP on January 23, and since then, our goal has been to help businesses streamline and manage their operations with greater efficiency, flexibility, and control. Since the launch, we've continued to enhance the platform every

    • Solution to Import OST File into Office 365.

      In today’s digital workplace, organizations are rapidly moving toward cloud-based email systems for better flexibility, security, and collaboration. Microsoft 365 has become one of the most widely used platforms for business communication. A common requirement

    • Zoho Contacts *Web Interface Does Not Load* (Tested in Firefox, Safari)

      When trying to load https://contacts.zoho.com the error shown in the console is: The resource from “https://static.zohocdn.com/zmail/zm/newContactsChange11/js/main.js” was blocked due to MIME type (“application/json”) mismatch (X-Content-Type-Options:

    • Admin-Side Calendar Delegation from the Admin Console (Parity with Zoho Mail Mailbox Delegation)

      Summary Zoho Mail already lets organization admins delegate a user's mailbox to another user directly from the Admin Console — no approval from the mailbox owner required (Users > select user > Mail Settings > Delegated to > + Add). Zoho Calendar has

    • How use .PK12 certifcate for sign

      Hello! Is it possible to use my personal digital certificate (as a COMMODO .pk12) to sign documents? Thank you

    • Blueprint - Mandatory file upload field

      Hi, File upload (as we as image upload) field cannot be set as mandatory during a blueprint transition. Is there a workaround? Setting attachments as mandatory doesn't solve this need as we have no control over which attachments are added, nor can we

    • Completed Calls don't associate with Scheduled Calls

      I schedule calls at specific times so that they are easily viewable on my phone. I open a given call on my phone and use the call icon at the bottom of the screen. I complete the call and select "yes" when asked if I want to log the call. I enter the

    • Integrations of freelancing websites

      It is a customized effort which we require to be implemented on our Zoho recruit. We want that Upwork and Freelancer and other such freelancing websites get integrated into our Zoho Recruit, so that, any communication which we do with the candidates from those websites gets directly recorded on our Zoho recruit and we don't have to move back and forth by opening any other application other than Zoho. If this can be done, we think of managing the entire communication through Zoho recruit and use it

    • Workflow Preventing others from editing

      Using workflows in WorkDrive to implement a document review process has been extremely helpful in my organization. The only problem is that other users who have access to the document via standard document sharing rules are unable to edit the document.

    • MCP > Creator connection failing with Claude

      I'm trying to get claude to access any of my Zoho Creator apps and it keeps failing. I have enabled all tools for creator and ensured in claude settings that everything is authorised. Here is what claude says : Unfortunately, the error messages I'm receiving

    • Zoho Analytics UI Bug

      Hello, all, The Aggregate Formulas in Zoho Analytics' list of fields have a 3-dot menu: If the formula has a long name, the name is not fully visible in the list, and a 3-dot menu is not accessible from it: This is not convenient, especially when the

    • Help me recover my account

      business@heymods.mobi is an account I registered two years ago. My domain is no longer valid, and I cannot access the admin page. I also subscribed to a $12 service, but I cannot configure the domain. Please help me set xunmeng.app@gmail.com as the admin,

    • I cannot receive emails

      I cannot receive email sent to my personal email account. I can send them but not receive them. I don't have a domain. Zoho direct email. Please help

    • I don't have access to my signup email.

      Hi, I don't have access to my signup email. I signed up while using the Loveabe app. I don't have access to the app that I built with the email ramonsepulveda@dreamgiftsfinder.com. Please help me cancel my account with you through that email.

    • Update on default settings for AI features in Cliq

      Hello all, We'd like to provide clarity on a recent change to AI feature defaults in Cliq. As part of our regular review of AI features conducted in April 2026, we re-evaluated how these features are enabled by default. We've decided that the AI features

    • Zoho CRM custom button function, how to add line breaks/ new lines in the return message

      When creating button function in CRM it requires a `return "";` Then when the button is client by the user a message pops up with what ever is returned from the function. But I want to have a message with multiple lines, meaning I need to add a line break

    • Email not Received

      No email has been recieved except welcome email and one more email in 2025.

    • i cant renew my domain bfftube.cloudns.cc

      i cant renew my domain bfftube.cloudns.cc because its a free subdomain from cloudns and you cant renew it its always active can some fix this becasue again there is no way to renew it becasue its free subdomain and again its always active

    • How to Switch from Outlook for Mac to Outlook for Windows

      The most often used file formats for users to manage crucial data are OLM and PST files. PST files keep a copy of data on the configured system from Outlook, while the OLM file contains the Mac Outlook data items, which are only accessible with Outlook

    • Different languages for users

      Hello, Do you plan to enable individual users to select their languages for interface? Currently language can be changed for everyone - it looks like a settings for a whole portal, which is not good when you are working internationally. Best regards,

    • Issues migrating Google email

      I am considering Zoho because Google will start charging for G Suite legacy free edition.    So, a key element in my decision is the ability to migrate as much from Google as possible.  I am giving email a try first, but after hours of trying, I can't

    • "Print" option of GET Expense Report API not working

      Hello! I have been trying to use the "print" option of the GET Expense Report API but it seems the option does not alter the output. Is there an issue with the API or am I using it wrong? Here's my request code, in Deluge: response = invokeurl [ url :"https://www.zohoapis.com/expense/v1/expensereports/"

    • Related List Expanded View in Zoho CRM: see more related records at a glance, filter and take bulk actions

      Hello everyone! Related lists show you the records connected to what you're working on: contacts under an account, activities tied to a deal, products linked to a quote. But until now, you could only see 10 records at a time. If you needed to filter results

    • How to automatically update a % field according to a dropdown field in the Quote table

      Hello there, I have following couples: Success % Status 0% NP 30% No Feedback 50% PR 80% Opp. Concreta 100% A I would like the Success % field (percent) to automatically update based on the item of the Status field (dropdown). The fields are within the

    • CRM iOS App Missing Tags support

      Hi, I remember reading either a tread on iOS (Maybe Later) & Android (i believe Now Supported) regarding “Tags” in the mobile apps unfortunately I can’t seem to find either. Could we clarify are “Tags” support coming to CRM iOS app as searching the forums

    • Marketing Tip #41: Add a clear value proposition to your homepage

      When someone lands on your homepage, they should understand what you sell and why it is worth exploring within 5 seconds. If your homepage is too vague, cluttered, or focused only on design, visitors may leave before they even start browsing. A strong

    • Zoho Writer adds conditional logic and AI assistance to formulas: A step toward dynamic document automation

      Hi users, We are excited to announce new formula enhancements in Zoho Writer. This includes: New string formulas: Use 12 new string functions to dynamically transform and manipulate text in documents and automation templates. Conditional formulas: Configure

    • What's New in Zoho Billing | June 2026

      Hello users! June brings a new set of updates to Zoho Billing designed to strengthen how you manage subscriptions, customise your records, and handle expense documentation. This month's highlights include a new one-time addon quoting workflow for subscriptions,

    • Next Page