diff --git a/api/index.md b/api/index.md
index feddcaa..3ddb388 100644
--- a/api/index.md
+++ b/api/index.md
@@ -11,6 +11,7 @@ Unofficial documentation for the Scratch API. See [root index](..) for more info
 * [`/proxy` API](proxy.md) - Miscellaneous utilities
 * [`/users` API](users.md) - Fetch user information
 * [`projects.` and `assets.` APIs](project_data.md) - Fetch code and assets used in projects
+* [`synthesis-service.` and `translation-service.` APIs](synth_trans.md) - Fetch translations and syntheses used by block extensions
 
 ### Object definitions
 
diff --git a/api/project_data.md b/api/project_data.md
index cbaad87..c3c605d 100644
--- a/api/project_data.md
+++ b/api/project_data.md
@@ -2,11 +2,15 @@
 
 These retrieve all of the data and files needed for a scratch project/file.
 
-### `GET cdn.projects.scratch.mit.edu/<project id>/`
+## `https://cdn.projects.scratch.mit.edu/`
+
+### `GET /<project id>/`
 
 Retrieves the projects JSON data, which is where all of the code for a scratch project is stored.
 
-### `GET cdn.assets.scratch.mit.edu/internalapi/asset/<md5 file>/get/`
+## `https://cdn.assets.scratch.mit.edu/`
+
+### `GET /internalapi/asset/<md5 file>/get/`
 
 Retrieves the asset with the given file name. An asset is a costume, sound or other file used in a project.  Each asset in each project has a unique md5 id, which is used for referencing and retrieving it. 
 
diff --git a/api/synth_trans.md b/api/synth_trans.md
new file mode 100644
index 0000000..b1ea119
--- /dev/null
+++ b/api/synth_trans.md
@@ -0,0 +1,25 @@
+# `synthesis-service.` and `translate-service.` APIs
+
+These retrieve the speech synthesis and translation results for their respective extensions.
+
+## `https://translate-service.scratch.mit.edu/`
+
+### `GET /translate?language=<locale>&text=<text>`
+
+Retrieves the translation of the input text in the given language. `locale` is generally a two-letter language code. Refer to [this gist](https://gist.github.com/towerofnix/d4369e64604c5a0d7dca94954a83ab35) for a list of supported languages, or check the exports from [`scratch-translate-extension-languages`](https://www.npmjs.com/package/scratch-translate-extension-languages).
+
+Uses Google Translate [as of Dec. 9, 2019](https://scratch.mit.edu/discuss/post/3778811).
+
+### `GET https://translate-service.scratch.mit.edu/supported`
+
+Retrieves a list of supported language codes for translating text.
+
+Legacy endpoint - still online, but [no longer used](https://github.com/scratchfoundation/scratch-vm/pull/1159).
+
+## `https://synthesis-service.scratch.mit.edu/`
+
+### `GET /synth?locale=<speech locale>&gender=<gender>&text=<text>`
+
+Retrieves the synthesis of the input text as an audio file. `gender` is either "male" or "female"; `speech locale` is a "speech synth locale" as described in [the extension's source code](https://github.com/scratchfoundation/scratch-vm/blob/489111f4d74909c2adac40ade1618f966ba30c34/src/extensions/scratch3_text2speech/index.js#L194-L341).
+
+Likely uses [Amazon Polly](https://aws.amazon.com/polly/).