> For the complete documentation index, see [llms.txt](https://developers.make.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.make.com/custom-apps-documentation/app-components/rpcs.md). # Remote Procedure Calls Remote Procedure Calls are used to retrieve live data from a service for an input field. You can use RPCs to retrieve dynamic options in a field to clarify the expected input for a user. For example, selecting a country in a dropdown could trigger an RPC to retrieve corresponding states or cities. These requests are invoked while the user interacts with the modules when building a scenario. ## Types of RPCs * [Dynamic fields RPCs](/custom-apps-documentation/app-components/rpcs/dynamic-fields-rpc.md) generate dynamic fields inside a module. * [Dynamic options RPCs](/custom-apps-documentation/app-components/rpcs/dynamic-options-rpc.md) dynamically fill the fields in a module. * [Dynamic sample RPCs](/custom-apps-documentation/app-components/rpcs/dynamic-sample-rpc.md) replace hard-coded samples that might become outdated quickly. ## Components ### Connection Every RPC must have the same connection that is used by the modules calling the RPC. {% hint style="warning" %} If a module with a connection references an RPC that has no connection attached (or a different one), the module fails to open with the error "Provided connection is not acceptable for this RPC." This applies to **all** RPCs referenced by the module, including [request-less](/custom-apps-documentation/component-blocks/api/request-less-communication.md) RPCs that only return static fields and never call the API. {% endhint %} If a module offers multiple connections, the RPCs it references must declare the same connection list. ### Communication Communication can be [request-less](/custom-apps-documentation/component-blocks/api/request-less-communication.md). As with modules, you can use [pagination](/custom-apps-documentation/component-blocks/api/pagination.md) in RPCs to iterate the records. ### Parameters [Parameters](/custom-apps-documentation/block-elements/parameters.md) from the modules are passed automatically to linked RPCs. ## Available IML variables The following IML variables are available to use anywhere in a module within IML strings.

Variable	Description
`now`	Current date and time with milliseconds in UTC timezone, in ISO 8601 format: `YYYY-MM-DDTHH:mm:ss.sssZ`.
`environment`	TBD
`temp`	Contains custom variables created using the `temp` directive. Example: `"temp": {` `"id": 123` `},` `"url": "/user/{{temp.id}}" // url === "/user/123"`
`parameters`	The module's input parameters collection (static and mappable).. The keys are the parameter `name` values, and the values are the data mapped by the user.
`connection`	The connection data collection (access token or API key and other values).
`common`	The collection defined in the app's Base common data. This will typically include the module 'timeout' limit and Client ID and secret when using OAuth 2.0 code grant connections.
`data`	The module's data collection.
`scenario`	TBD
`metadata.expect`	The module's raw mappable parameters as they were specified in the configuration.
`metadata.interface`	The module’s raw interface array the way you have specified it in the configuration.

Additional variables available within the `response` collection:

Variable	Description
`output`	When using the wrapper directive, the 'output' variable represents the result of the output directive.

Additional variables available when using the `iterate` directive, for example within the wrapper or [pagination](/custom-apps-documentation/component-blocks/api/pagination.md) collections:

Variable	Description
`iterate.container.first`	The first item of the iterated array.
`iterate.container.last`	The last item of the iterated array.

Additional variables available within the [pagination](/custom-apps-documentation/component-blocks/api/pagination.md) and [response](/custom-apps-documentation/component-blocks/api/handling-responses.md) collections:

Variable	Description
`body`	The response body received from the last request.
`headers`	The response headers received from the last request.
`item`	When using the `iterative` directive, this variable represents the current item that is being iterated.

Additional variables available in the webhook [attach](/custom-apps-documentation/app-components/webhooks/dedicated/attached.md) RPC.

Variable	Description
`webhook.id`	Internal webhook ID.
`webhook.url`	The webhook URL that you can use to automatically register the webhook in the external platform via the API, when it's supported.

Additional variables available in the webhook [detach](/custom-apps-documentation/app-components/webhooks/dedicated/not-attached.md) RPC and in the `expect` [mappable parameter](/custom-apps-documentation/component-blocks/mappable-parameters.md) and the [interface](/custom-apps-documentation/component-blocks/interface.md) section of an instant trigger module.

Variable	Description
`webhook`	The webhook’s data collection.

## Limits

Name	Total limit of...	Value
Max Execution Timeout	... seconds	40

Name	Recommended limit of ...	Value
Request Count	... calls performed by RPC	3
Record Count	... paginated records	3 * number of objects per page

## Best Practices Review the [best practices for RPCs](/custom-apps-documentation/best-practices/remote-procedure-calls.md). --- # 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 dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://developers.make.com/custom-apps-documentation/app-components/rpcs.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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.