diff --git a/pkg/tools/skills_install.go b/pkg/tools/skills_install.go
index c7db02eb3..19a34d1cc 100644
--- a/pkg/tools/skills_install.go
+++ b/pkg/tools/skills_install.go
@@ -156,6 +156,19 @@ func (t *InstallSkillTool) Execute(ctx context.Context, args map[string]any) *To
 		return ErrorResult(fmt.Sprintf("skill %q is flagged as malicious and cannot be installed", slug))
 	}
 
+	if !workspaceHasValidInstalledSkill(t.workspace, dirName) {
+		rmErr := os.RemoveAll(targetDir)
+		if rmErr != nil {
+			logger.ErrorCF("tool", "Failed to remove invalid installed skill",
+				map[string]any{
+					"tool":       "install_skill",
+					"target_dir": targetDir,
+					"error":      rmErr.Error(),
+				})
+		}
+		return ErrorResult(fmt.Sprintf("failed to install %q: registry archive is not a valid skill", slug))
+	}
+
 	// Write origin metadata.
 	if err := writeOriginMeta(targetDir, registry, slug, result.Version); err != nil {
 		logger.ErrorCF("tool", "Failed to write origin metadata",
@@ -224,3 +237,16 @@ func writeOriginMeta(targetDir string, registry skills.SkillRegistry, slug, vers
 	// Use unified atomic write utility with explicit sync for flash storage reliability.
 	return fileutil.WriteFileAtomic(filepath.Join(targetDir, ".skill-origin.json"), data, 0o600)
 }
+
+func workspaceHasValidInstalledSkill(workspace, directory string) bool {
+	loader := skills.NewSkillsLoader(workspace, "", "")
+	for _, skill := range loader.ListSkills() {
+		if skill.Source != "workspace" {
+			continue
+		}
+		if filepath.Base(filepath.Dir(skill.Path)) == directory {
+			return true
+		}
+	}
+	return false
+}
diff --git a/pkg/tools/skills_install_test.go b/pkg/tools/skills_install_test.go
index 9ecf34ea3..7e051368d 100644
--- a/pkg/tools/skills_install_test.go
+++ b/pkg/tools/skills_install_test.go
@@ -15,6 +15,8 @@ import (
 
 type mockInstallRegistry struct{}
 
+const validSkillMarkdown = "---\nname: pr-review\ndescription: Review pull requests\n---\n# PR Review\n"
+
 func (m *mockInstallRegistry) Name() string { return "clawhub" }
 
 func (m *mockInstallRegistry) ResolveInstallDirName(target string) (string, error) {
@@ -32,11 +34,17 @@ func (m *mockInstallRegistry) GetSkillMeta(context.Context, string) (*skills.Ski
 }
 
 func (m *mockInstallRegistry) DownloadAndInstall(
-	context.Context,
-	string,
-	string,
-	string,
+	_ context.Context,
+	_ string,
+	_ string,
+	targetDir string,
 ) (*skills.InstallResult, error) {
+	if err := os.MkdirAll(targetDir, 0o755); err != nil {
+		return nil, err
+	}
+	if err := os.WriteFile(filepath.Join(targetDir, "SKILL.md"), []byte(validSkillMarkdown), 0o600); err != nil {
+		return nil, err
+	}
 	return &skills.InstallResult{Version: "test"}, nil
 }
 
@@ -59,11 +67,17 @@ func (m *mockGitHubInstallRegistry) GetSkillMeta(context.Context, string) (*skil
 }
 
 func (m *mockGitHubInstallRegistry) DownloadAndInstall(
-	context.Context,
-	string,
-	string,
-	string,
+	_ context.Context,
+	_ string,
+	_ string,
+	targetDir string,
 ) (*skills.InstallResult, error) {
+	if err := os.MkdirAll(targetDir, 0o755); err != nil {
+		return nil, err
+	}
+	if err := os.WriteFile(filepath.Join(targetDir, "SKILL.md"), []byte(validSkillMarkdown), 0o600); err != nil {
+		return nil, err
+	}
 	return &skills.InstallResult{Version: "main"}, nil
 }
 
@@ -72,14 +86,57 @@ type stubGitHubInstallRegistry struct {
 }
 
 func (m *stubGitHubInstallRegistry) DownloadAndInstall(
-	context.Context,
-	string,
-	string,
-	string,
+	_ context.Context,
+	_ string,
+	_ string,
+	targetDir string,
 ) (*skills.InstallResult, error) {
+	if err := os.MkdirAll(targetDir, 0o755); err != nil {
+		return nil, err
+	}
+	if err := os.WriteFile(filepath.Join(targetDir, "SKILL.md"), []byte(validSkillMarkdown), 0o600); err != nil {
+		return nil, err
+	}
 	return &skills.InstallResult{Version: "main"}, nil
 }
 
+type mockInvalidInstallRegistry struct{}
+
+func (m *mockInvalidInstallRegistry) Name() string { return "clawhub" }
+
+func (m *mockInvalidInstallRegistry) ResolveInstallDirName(target string) (string, error) {
+	return target, nil
+}
+
+func (m *mockInvalidInstallRegistry) SkillURL(slug, _ string) string { return slug }
+
+func (m *mockInvalidInstallRegistry) Search(context.Context, string, int) ([]skills.SearchResult, error) {
+	return nil, nil
+}
+
+func (m *mockInvalidInstallRegistry) GetSkillMeta(context.Context, string) (*skills.SkillMeta, error) {
+	return nil, nil
+}
+
+func (m *mockInvalidInstallRegistry) DownloadAndInstall(
+	_ context.Context,
+	_ string,
+	_ string,
+	targetDir string,
+) (*skills.InstallResult, error) {
+	if err := os.MkdirAll(targetDir, 0o755); err != nil {
+		return nil, err
+	}
+	if err := os.WriteFile(
+		filepath.Join(targetDir, "SKILL.md"),
+		[]byte("---\nname: bad_skill\ndescription: invalid name\n---\n# Invalid\n"),
+		0o600,
+	); err != nil {
+		return nil, err
+	}
+	return &skills.InstallResult{Version: "test"}, nil
+}
+
 func TestInstallSkillToolName(t *testing.T) {
 	tool := NewInstallSkillTool(skills.NewRegistryManager(), t.TempDir())
 	assert.Equal(t, "install_skill", tool.Name())
@@ -209,3 +266,20 @@ func TestInstallSkillToolAllowsGitHubURLSlug(t *testing.T) {
 	assert.Equal(t, "main", meta.InstalledVersion)
 	assert.NotZero(t, meta.InstalledAt)
 }
+
+func TestInstallSkillToolRejectsInvalidInstalledSkill(t *testing.T) {
+	workspace := t.TempDir()
+	registryMgr := skills.NewRegistryManager()
+	registryMgr.AddRegistry(&mockInvalidInstallRegistry{})
+	tool := NewInstallSkillTool(registryMgr, workspace)
+
+	result := tool.Execute(context.Background(), map[string]any{
+		"slug":     "broken-skill",
+		"registry": "clawhub",
+	})
+
+	assert.True(t, result.IsError)
+	assert.Contains(t, result.ForLLM, "not a valid skill")
+	_, err := os.Stat(filepath.Join(workspace, "skills", "broken-skill"))
+	assert.True(t, os.IsNotExist(err))
+}