# Clickatell API Reference ## Channels * [WhatsApp and SMS (One API)](/developers-api-reference/reference/one-api.md): Communicate with customers via multiple messaging channels (WhatsApp and SMS) using a single integration. * [SMS only](/developers-api-reference/sms-api.md): Enable one- and two-way SMS communication with your customers. ## Applications * [Chat 2 Pay](/developers-api-reference/chat-2-pay-api.md): Send payment requests to customers and facilitate payments via chat for secure, contactless payment experiences. * [Chat Flow](/developers-api-reference/chat-flow.md): Direct customers to an external web page from within a Chat Flow conversation and return with additional data. --- # Agent Instructions: 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: ``` GET https://help.clickatell.com/developers-api-reference/reference/clickatell-api-reference.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.