diff --git a/prompts/01-01-01-tag.md b/prompts/01-01-01-tag.md
index 17e97c0..b8a265f 100644
--- a/prompts/01-01-01-tag.md
+++ b/prompts/01-01-01-tag.md
@@ -14,6 +14,8 @@ Rules:
 - For each keyword, quote 1 to 3 verbatim lines of the lyrics
   that ground it; do not give a keyword you cannot ground.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON object mapping each keyword to its list
 of quotes, and nothing else:
 
diff --git a/prompts/01-02-01-merge.md b/prompts/01-02-01-merge.md
index 27b0fe1..9db3561 100644
--- a/prompts/01-02-01-merge.md
+++ b/prompts/01-02-01-merge.md
@@ -17,6 +17,8 @@ Rules:
   by hyphens, that best names the theme it gathers.  Group
   names must be unique.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON object mapping each group name to the
 list of its member keywords, and nothing else:
 
diff --git a/prompts/01-03-01-cap.md b/prompts/01-03-01-cap.md
index 71f21ac..9a73867 100644
--- a/prompts/01-03-01-cap.md
+++ b/prompts/01-03-01-cap.md
@@ -20,6 +20,8 @@ Rules:
   by hyphens, that best names the theme it gathers.  Group
   names must be unique.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON object mapping each group name to the
 list of its member keywords, and nothing else:
 
diff --git a/prompts/01-04-01-code.md b/prompts/01-04-01-code.md
index 3a161c5..ca0bf20 100644
--- a/prompts/01-04-01-code.md
+++ b/prompts/01-04-01-code.md
@@ -21,6 +21,8 @@ Rules:
   the lyrics that ground it; do not assign a keyword you
   cannot ground.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON object mapping each assigned keyword to
 its list of quotes (an empty object when no keyword applies),
 and nothing else:
diff --git a/prompts/01-04-02-code-arb.md b/prompts/01-04-02-code-arb.md
index 92133cd..28641ed 100644
--- a/prompts/01-04-02-code-arb.md
+++ b/prompts/01-04-02-code-arb.md
@@ -30,6 +30,8 @@ Rules:
   lines of the lyrics; quote them.
 - Do not add any keyword that is not listed.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON object mapping each kept keyword to your
 list of quotes, and nothing else.  A dropped keyword is simply
 left out; output an empty object when nothing is kept:
diff --git a/prompts/02-01-01-screen.md b/prompts/02-01-01-screen.md
index 1938733..1c17326 100644
--- a/prompts/02-01-01-screen.md
+++ b/prompts/02-01-01-screen.md
@@ -12,6 +12,8 @@ Rules:
   lines of the lyrics that ground the judgment; if you cannot
   ground it in a quote, the answer is no.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON array and nothing else: the quoted
 lines when the song expresses the theme, or an empty array
 when it does not:
diff --git a/prompts/02-01-02-screen-arb.md b/prompts/02-01-02-screen-arb.md
index 0bab97a..cd844d7 100644
--- a/prompts/02-01-02-screen-arb.md
+++ b/prompts/02-01-02-screen-arb.md
@@ -21,6 +21,8 @@ Rules:
   lines of the lyrics that ground the judgment; if you cannot
   ground it in a quote, the answer is no.
 
+Do not wrap the output in a Markdown code fence.
+
 Output a single JSON array and nothing else: the quoted
 lines when the song expresses the theme, or an empty array
 when it does not: