# Custom There may be cases where the [inference runtimes](/mlserver/runtimes.md) offered out-of-the-box by MLServer may not be enough, or where you may need **extra custom functionality** which is not included in MLServer (e.g. custom codecs). To cover these cases, MLServer lets you create custom runtimes very easily. To learn more about how you can write custom runtimes with MLServer, check out the [Custom Runtimes user guide](/mlserver/user-guide/custom.md). Alternatively, you can also see this [end-to-end example](/mlserver/examples/custom.md) which walks through the process of writing a custom runtime. --- # 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://docs.seldon.ai/mlserver/runtimes/custom.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.