docs: document agent access over MCP and token tag restrictions

2026-09-09 08:20:42 +00:00
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@@ -83,6 +83,17 @@ one, create a replacement and revoke the old key.
 Restricted keys show their tags as chips beside their scopes in the list.
 Unrestricted keys show nothing there, which is the common case.

+The restriction applies to every API token, not only ones handed to an
+[MCP agent](../vantage/mcp.md). A CI token, a monitoring script's token and
+an agent's token are all held to the same tag scope check wherever the
+service layer resolves servers — the mechanism does not know or care what
+kind of caller is holding the token.
+
+Nor can a token created under a restricted token reach further than its
+creator: minting a new key from an already-restricted key can only narrow
+the tag set, never widen or drop it. A `env=staging` token cannot mint a
+token that also sees production.
+
 ## Reading the key list

 Each key is one record rather than a row of bare strings: