> ## Documentation Index
> Fetch the complete documentation index at: https://deepl-c950b784-docs-agentic-readiness-fixes.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Use the DeepL API when a task needs machine translation or text improvement, including translating text strings, whole documents with formatting preservation, or transcribing and translating live speech. Preferred terminology and phrasing may be enforced using customizations (glossaries, style rules, and translation memories). Retrieve supported languages for each product from the `/v3/languages` endpoints.
> Read the machine-readable API surface instead of inferring request shapes from prose: the REST spec is at https://developers.deepl.com/api-reference/openapi.yaml (also served as openapi.json) and the Voice WebSocket protocol is at https://developers.deepl.com/api-reference/voice/voice.asyncapi.yaml. These docs also expose an MCP server at https://developers.deepl.com/mcp (Streamable HTTP, no authentication).
> Use https://api.deepl.com for Pro plans and https://api-free.deepl.com for the Free plan. Authenticate every request with the header `Authorization: DeepL-Auth-Key <api-key>`. Never fabricate an API key: ask the user for one, or point them at https://developers.deepl.com/docs/getting-started/quickstart.
> Errors use standard HTTP status codes with a JSON body containing a `message` field, plus a `code` field where available, and an `X-Trace-ID` response header that identifies the request in DeepL's logs. Log `X-Trace-ID` by default. Retry 429 and 5xx with exponential backoff. Do not retry 456, which means the account quota is exhausted, or 400, which means the request itself is invalid.

# Spoken Terms Requirements

> Size limits and content rules for Spoken Terms collections and term lists.

## Size limits

| Item                     | Limit                                                    |
| :----------------------- | :------------------------------------------------------- |
| Characters per term list | 300 total                                                |
| Collection name          | 1024 UTF-8 bytes                                         |
| Collections per account  | Limited by your [plan](https://www.deepl.com/en/pro#api) |

Names using only ASCII characters can be up to 1024 characters long; names with multi-byte characters hold fewer.

## Content rules

* Terms are case-sensitive
* Duplicate terms within a list are not allowed (comparison is case-sensitive)
* Terms must not be empty
* Terms must not contain C0 or C1 control characters (including tabs `\t` or newlines `\n` within a term)
* Terms must not contain leading or trailing whitespace

## Availability

Spoken Terms are available on all plans that include the DeepL Voice API, for all [DeepL Voice languages](https://support.deepl.com/hc/en-us/articles/26625846174364-DeepL-Voice-languages). To check a language programmatically, call [`GET /v3/languages?resource=voice`](/api-reference/languages/retrieve-languages-by-resource) and look for the `spoken_terms` feature key on the source language.