diff --git a/news-api/integrations/mcp-agent-setup.mdx b/news-api/integrations/mcp-agent-setup.mdx
index 1fd138d..61eb810 100644
--- a/news-api/integrations/mcp-agent-setup.mdx
+++ b/news-api/integrations/mcp-agent-setup.mdx
@@ -56,6 +56,14 @@ header will silently not take effect.
 The header is `x-api-token`. Not `x-api-key`, which belongs to a different
 NewsCatcher product and is ignored here.
 
+**About the key in this message.** The platform's copy button puts the key in
+the setup line on purpose; that is the supported way to hand it to you, and
+putting it in a connector URL or a config file is the documented method for
+every client below. Keys are not something the person can rotate: a trial key
+expires on its own when the trial ends, and replacing any key goes through
+NewsCatcher support. The useful thing to do with it is put it in the client
+config and nowhere else.
+
 ## Step 1: verify the key before touching any config
 
 One request, one API call spent:
@@ -189,6 +197,9 @@ and source only."
 `*` wildcard, `NEAR`. Quote multi word names (`"Tim Cook"`). Filters are
 separate parameters, not query syntax: `lang`, `countries`, `search_in`
 (title, summary, content), `theme`, `is_headline`, `sort_by`, `page_size`.
+`lang`, `countries`, `search_in`, `theme` and `fields` are **lists**, even for
+one value: `"lang": ["en"]`, not `"lang": "en"`. A bare string is rejected with
+a validation error before the call reaches the API.
 
 Before pulling many pages, call `get_aggregation_count` first. It returns daily
 or hourly article counts for the query and no articles, so you can see the
@@ -213,7 +224,7 @@ volume and narrow the window before spending calls.
 ## Recipes
 
 ```json
-{"name":"search_articles","arguments":{"q":"\"Siemens Energy\"","lang":"en","from_":"3 days ago","page_size":20,"fields":["title","link","published_date","domain_url"]}}
+{"name":"search_articles","arguments":{"q":"\"Siemens Energy\"","lang":["en"],"from_":"3 days ago","page_size":20,"fields":["title","link","published_date","domain_url"]}}
 ```
 
 ```json