fix: use block-style YAML sequences in SKILL.md frontmatter (#580)

Replace flow sequences (bins: ["gws"], skills: [...]) with block-style
sequences in all generated SKILL.md frontmatter templates.

Flow sequences are valid YAML but rejected by strictyaml, which the
Agent Skills reference implementation (agentskills validate) uses to
parse frontmatter. This caused all 93 generated skills to fail
validation.

Also adds unit tests verifying that service, shared, persona, and
recipe skill templates produce block-style sequences only.

Fixes #521

.changeset/fix-skill-frontmatter-flow-sequences.md

@@ -0,0 +1,14 @@
+---
+"@googleworkspace/cli": patch
+---
+
+fix: use block-style YAML sequences in generated SKILL.md frontmatter
+
+Replace flow sequences (`bins: ["gws"]`, `skills: [...]`) with block-style
+sequences (`bins:\n  - gws`) in all generated SKILL.md frontmatter templates.
+
+Flow sequences are valid YAML but rejected by `strictyaml`, which the
+Agent Skills reference implementation (`agentskills validate`) uses to parse
+frontmatter. This caused all 93 generated skills to fail validation.
+
+Fixes #521

src/generate_skills.rs

@@ -391,7 +391,8 @@ metadata:
   openclaw:
     category: "productivity"
     requires:
-      bins: ["gws"]
+      bins:
+        - gws
     cliHelp: "gws {alias} --help"
 ---
 
@@ -527,7 +528,8 @@ metadata:
   openclaw:
     category: "{category}"
     requires:
-      bins: ["gws"]
+      bins:
+        - gws
     cliHelp: "gws {alias} {cmd_name} --help"
 ---
 
@@ -674,7 +676,8 @@ metadata:
   openclaw:
     category: "productivity"
     requires:
-      bins: ["gws"]
+      bins:
+        - gws
 ---
 
 # gws — Shared Reference
@@ -755,13 +758,13 @@ gws <service> <resource> [sub-resource] <method> [flags]
 fn render_persona_skill(persona: &PersonaEntry) -> String {
     let mut out = String::new();
 
-    // metadata JSON string for skills array
+    // Block-style YAML for skills array
     let required_skills = persona
         .services
         .iter()
-        .map(|s| format!("\"gws-{s}\""))
+        .map(|s| format!("        - gws-{s}"))
         .collect::<Vec<_>>()
-        .join(", ");
+        .join("\n");
 
     let trigger_desc = truncate_desc(&persona.description);
 
@@ -774,8 +777,10 @@ metadata:
   openclaw:
     category: "persona"
     requires:
-      bins: ["gws"]
-      skills: [{skills}]
+      bins:
+        - gws
+      skills:
+{skills}
 ---
 
 # {title}
@@ -829,9 +834,9 @@ fn render_recipe_skill(recipe: &RecipeEntry) -> String {
     let required_skills = recipe
         .services
         .iter()
-        .map(|s| format!("\"gws-{s}\""))
+        .map(|s| format!("        - gws-{s}"))
         .collect::<Vec<_>>()
-        .join(", ");
+        .join("\n");
 
     let trigger_desc = truncate_desc(&recipe.description);
 
@@ -845,8 +850,10 @@ metadata:
     category: "recipe"
     domain: "{category}"
     requires:
-      bins: ["gws"]
-      skills: [{skills}]
+      bins:
+        - gws
+      skills:
+{skills}
 ---
 
 # {title}
@@ -1187,4 +1194,188 @@ mod tests {
     fn test_product_name_from_title_adds_google() {
         assert_eq!(product_name_from_title("Drive API"), "Google Drive");
     }
+
+    /// Extract the YAML frontmatter (between `---` delimiters) from a skill string.
+    fn extract_frontmatter(content: &str) -> &str {
+        let content = content.strip_prefix("---").expect("no opening ---");
+        let (frontmatter, _) = content.split_once("\n---").expect("no closing ---");
+        frontmatter
+    }
+
+    /// Asserts that the frontmatter uses block-style YAML sequences.
+    ///
+    /// Detects flow sequences by checking whether YAML values start with `[`,
+    /// rather than looking for brackets anywhere in a line.  This avoids false
+    /// positives from string values that legitimately contain brackets
+    /// (e.g., `description: 'Note: [INTERNAL] ticket was filed'`).
+    fn assert_block_style_sequences(frontmatter: &str) {
+        for (i, line) in frontmatter.lines().enumerate() {
+            let trimmed = line.trim();
+            // Skip lines that don't look like YAML values (e.g., comments, empty)
+            if trimmed.is_empty() || trimmed.starts_with('#') {
+                continue;
+            }
+            // A YAML flow sequence is "key: [...]". Check the value after `:`.
+            if let Some(colon_pos) = trimmed.find(':') {
+                let value = trimmed[colon_pos + 1..].trim();
+                // A flow sequence is not quoted. A quoted string is a scalar.
+                let is_quoted = value.starts_with('"') || value.starts_with('\'');
+                assert!(
+                    is_quoted || !value.starts_with('['),
+                    "Flow sequence found on line {} of frontmatter: {:?}\n\
+                     Use block-style sequences instead (e.g., `- value`)",
+                    i + 1,
+                    trimmed
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn test_service_skill_frontmatter_uses_block_sequences() {
+        let entry = &services::SERVICES[0]; // first service
+        let doc = crate::discovery::RestDescription {
+            name: entry.api_name.to_string(),
+            title: Some("Test API".to_string()),
+            description: Some(entry.description.to_string()),
+            ..Default::default()
+        };
+        let cli = crate::commands::build_cli(&doc);
+        let helpers: Vec<&Command> = cli
+            .get_subcommands()
+            .filter(|s| s.get_name().starts_with('+'))
+            .collect();
+        let resources: Vec<&Command> = cli
+            .get_subcommands()
+            .filter(|s| !s.get_name().starts_with('+'))
+            .collect();
+        let product_name = product_name_from_title("Test API");
+        let md = render_service_skill(
+            entry.aliases[0],
+            entry,
+            &helpers,
+            &resources,
+            &product_name,
+            &doc,
+        );
+        let fm = extract_frontmatter(&md);
+        assert_block_style_sequences(fm);
+        assert!(
+            fm.contains("bins:\n"),
+            "frontmatter should contain 'bins:' on its own line"
+        );
+        assert!(
+            fm.contains("- gws"),
+            "frontmatter should contain '- gws' block entry"
+        );
+    }
+
+    #[test]
+    fn test_shared_skill_frontmatter_uses_block_sequences() {
+        let tmp = tempfile::tempdir().unwrap();
+        generate_shared_skill(tmp.path()).unwrap();
+        let content = std::fs::read_to_string(tmp.path().join("gws-shared/SKILL.md")).unwrap();
+        let fm = extract_frontmatter(&content);
+        assert_block_style_sequences(fm);
+        assert!(
+            fm.contains("- gws"),
+            "shared skill frontmatter should contain '- gws'"
+        );
+    }
+
+    #[test]
+    fn test_persona_skill_frontmatter_uses_block_sequences() {
+        let persona = PersonaEntry {
+            name: "test-persona".to_string(),
+            title: "Test Persona".to_string(),
+            description: "A test persona for unit tests.".to_string(),
+            services: vec!["gmail".to_string(), "calendar".to_string()],
+            workflows: vec![],
+            instructions: vec!["Do this.".to_string()],
+            tips: vec![],
+        };
+        let md = render_persona_skill(&persona);
+        let fm = extract_frontmatter(&md);
+        assert_block_style_sequences(fm);
+        assert!(
+            fm.contains("- gws"),
+            "persona frontmatter should contain '- gws'"
+        );
+        assert!(
+            fm.contains("- gws-gmail"),
+            "persona frontmatter should contain '- gws-gmail'"
+        );
+        assert!(
+            fm.contains("- gws-calendar"),
+            "persona frontmatter should contain '- gws-calendar'"
+        );
+    }
+
+    #[test]
+    fn test_recipe_skill_frontmatter_uses_block_sequences() {
+        let recipe = RecipeEntry {
+            name: "test-recipe".to_string(),
+            title: "Test Recipe".to_string(),
+            description: "A test recipe for unit tests.".to_string(),
+            category: "testing".to_string(),
+            services: vec!["drive".to_string(), "sheets".to_string()],
+            steps: vec!["Step one.".to_string()],
+            caution: None,
+        };
+        let md = render_recipe_skill(&recipe);
+        let fm = extract_frontmatter(&md);
+        assert_block_style_sequences(fm);
+        assert!(
+            fm.contains("- gws"),
+            "recipe frontmatter should contain '- gws'"
+        );
+        assert!(
+            fm.contains("- gws-drive"),
+            "recipe frontmatter should contain '- gws-drive'"
+        );
+        assert!(
+            fm.contains("- gws-sheets"),
+            "recipe frontmatter should contain '- gws-sheets'"
+        );
+    }
+
+    #[test]
+    fn test_helper_skill_frontmatter_uses_block_sequences() {
+        // Use a service known to have helpers, e.g., drive
+        let entry = services::SERVICES
+            .iter()
+            .find(|s| s.api_name == "drive")
+            .unwrap();
+
+        let doc = crate::discovery::RestDescription {
+            name: entry.api_name.to_string(),
+            title: Some("Test API".to_string()),
+            description: Some(entry.description.to_string()),
+            ..Default::default()
+        };
+        let cli = crate::commands::build_cli(&doc);
+        let helper = cli
+            .get_subcommands()
+            .find(|s| s.get_name().starts_with('+'))
+            .expect("No helper command found for test");
+
+        let product_name = product_name_from_title("Test API");
+        let md = render_helper_skill(
+            entry.aliases[0],
+            helper.get_name(),
+            helper,
+            entry,
+            &product_name,
+        );
+        let fm = extract_frontmatter(&md);
+        assert_block_style_sequences(fm);
+        assert!(
+            fm.contains("bins:\n"),
+            "frontmatter should contain 'bins:' on its own line"
+        );
+        assert!(
+            fm.contains("- gws"),
+            "frontmatter should contain '- gws' block entry"
+        );
+    }
 }