> For the complete documentation index, see [llms.txt](https://docs.welkinhealth.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.welkinhealth.com/designer/custom-data-types/cdt-configuration.md). # CDT Configuration Custom Data Types (CDTs) are one of the cornerstones for customization in Welkin, allowing for the entry of data points used throughout the platform. ## What are Custom Data Types? CDTs allow for the entry of data points that may be used throughout Welkin. When creating a new CDT, think of the CDT name as the folder name and the data fields created within it (CDTFs) as sub-categories of that folder. CDTs are created in Designer under **Custom Data → Data Types**. Click **+New** in the Data Types screen. From here, enter the CDT name (the "folder name") and then enter a data field name (the "sub-folder"). Select the type of data the field will contain from the dropdown — many options are available. Certain selections will reveal additional options for that field. For example, selecting **Boolean** will add a field asking whether it should be a radio button or checkbox. Continue adding fields by clicking **+ Data Field** at the bottom of the previous field. ## Using CDTs Once created, CDTs can be used across Welkin. The most common use is in Forms and Assessments — a question is entered, a Data Type is selected from the dropdown, and then the specific Data Field is chosen. That field will record the patient's answer during the assessment. For more information on creating Assessments, see [Create an Assessment or Form Template](/designer/documents-and-assessments/how-to-create-an-assessment-or-form-template.md). ## Considerations * When a CDT is referenced in an Assessment, it writes a value to **all CDTFs** regardless of which are surfaced in the assessment * A Data View for a CDT can only surface values from one CDT — multiple CDTs cannot be combined into a single Data View * Creating any CDTs will require updates to your current Security Policies * **CDT names cannot be changed once created** * **CDTF settings cannot be changed after creation** (e.g., a list type field cannot later be changed to free text) * Think through the above considerations and the end result of the data collected before creating CDTs ## Formulas Formulas are a specific CDTF type that calculates values based on other CDTFs within the same CDT. For example, a patient Assessment that records height and weight into two CDTFs can use a third Formula CDTF to calculate and store BMI, which can then be displayed in a Data View. For more information, see [Create Formulaic Custom Data Type Fields](/designer/custom-data-types/create-formulaic-custom-data-type-fields.md). *** More Questions? Contact or your Implementation/CSM directly. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.welkinhealth.com/designer/custom-data-types/cdt-configuration.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.