diff --git a/prompts/01-01-01-tag.md b/prompts/01-01-01-tag.md
index b8a265f..b5cd02f 100644
--- a/prompts/01-01-01-tag.md
+++ b/prompts/01-01-01-tag.md
@@ -15,6 +15,8 @@ Rules:
   that ground it; do not give a keyword you cannot ground.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 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 9db3561..0e85508 100644
--- a/prompts/01-02-01-merge.md
+++ b/prompts/01-02-01-merge.md
@@ -18,6 +18,8 @@ Rules:
   names must be unique.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 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 9a73867..a8bb05c 100644
--- a/prompts/01-03-01-cap.md
+++ b/prompts/01-03-01-cap.md
@@ -21,6 +21,8 @@ Rules:
   names must be unique.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 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 ca0bf20..17daa10 100644
--- a/prompts/01-04-01-code.md
+++ b/prompts/01-04-01-code.md
@@ -22,6 +22,8 @@ Rules:
   cannot ground.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 Output a single JSON object mapping each assigned keyword to
 its list of quotes (an empty object when no keyword applies),
diff --git a/prompts/01-04-02-code-arb.md b/prompts/01-04-02-code-arb.md
index 28641ed..fe3af89 100644
--- a/prompts/01-04-02-code-arb.md
+++ b/prompts/01-04-02-code-arb.md
@@ -31,6 +31,8 @@ Rules:
 - Do not add any keyword that is not listed.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 Output a single JSON object mapping each kept keyword to your
 list of quotes, and nothing else.  A dropped keyword is simply
diff --git a/prompts/02-01-01-screen.md b/prompts/02-01-01-screen.md
index 1c17326..d0e673e 100644
--- a/prompts/02-01-01-screen.md
+++ b/prompts/02-01-01-screen.md
@@ -13,6 +13,8 @@ Rules:
   ground it in a quote, the answer is no.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 Output a single JSON array and nothing else: the quoted
 lines when the song expresses the theme, or an empty array
diff --git a/prompts/02-01-02-screen-arb.md b/prompts/02-01-02-screen-arb.md
index cd844d7..794b6dc 100644
--- a/prompts/02-01-02-screen-arb.md
+++ b/prompts/02-01-02-screen-arb.md
@@ -22,6 +22,8 @@ Rules:
   ground it in a quote, the answer is no.
 
 Do not wrap the output in a Markdown code fence.
+The output must be valid JSON; escape any double quote
+inside a string as \".
 
 Output a single JSON array and nothing else: the quoted
 lines when the song expresses the theme, or an empty array