Allowed reading plain text and JSON from the web, with a stronger prompt injection filter (#1000)

documentation/Tools.md

@@ -86,7 +86,9 @@ The prompt-level warning in `systemPromptInstructions` — that everything a too
 
 ## Reading Web Pages
 
-`web_search` and `read_web_page` both load pages, and so does the `ReadWebContent` component the assistants offer. All three go through `WebPageRetrievalService` — every page AI Studio reads goes through that one service. It validates DNS results and every redirect target before connecting, binds the connection to the validated addresses, caps the response size, and accepts only HTML.
+`web_search` and `read_web_page` both load pages, and so does the `ReadWebContent` component the assistants offer. All three go through `WebPageRetrievalService` — every page AI Studio reads goes through that one service. It validates DNS results and every redirect target before connecting, binds the connection to the validated addresses, and caps the response size.
+
+The service reads HTML pages and text documents. An HTML page has its main content extracted and converted to Markdown. A text document — plain text, JSON, XML, YAML, CSV, and similar formats — comes back as the server sent it, with only its line endings unified; `RetrievedWebPage.ContentKind` tells the two apart, which matters because a short text document is complete while a short extracted page usually is not. Binary content such as PDFs or images is refused as soon as the response headers arrive, before its body is downloaded. Both kinds go through the same prompt-injection filter, after truncation, in every caller; the runtime's filter also decodes the escapes of JSON and XML, such as `\u0049` or `I`, because a model reads them as the characters they stand for.
 
 What differs between callers is which targets are acceptable, and that follows from who chose the URL. `web_search` uses the public-only policy and never reads private, loopback, or link-local targets. `read_web_page` may reach an explicitly allowed private host, and only for a High-confidence provider. The `ReadWebContent` component sets `TargetChosenByUser`, which lifts the target restrictions entirely: the user typed the address, so their own network and a local server are legitimate. Never set that flag for a URL that reached AI Studio through a model.