diff --git a/packages/language/src/blocks.ts b/packages/language/src/blocks.ts
index 3aeea21..4843e07 100644
--- a/packages/language/src/blocks.ts
+++ b/packages/language/src/blocks.ts
@@ -118,7 +118,7 @@ export const ActionBlock = NamedBlock(
     label: StringValue.describe('Display label shown in the UI.'),
     inputs: InputsBlock,
     outputs: OutputsBlock,
-    target: StringValue.describe(
+    target: StringValue.required().describe(
       'External implementation target URI (e.g., "flow://Action_Name").'
     ),
     source: StringValue.describe(
diff --git a/packages/language/src/lint/required-fields.test.ts b/packages/language/src/lint/required-fields.test.ts
new file mode 100644
index 0000000..ab0f164
--- /dev/null
+++ b/packages/language/src/lint/required-fields.test.ts
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2026, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ * For full license text, see the LICENSE file in the repo root or https://www.apache.org/licenses/LICENSE-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { parse } from '@agentscript/parser';
+import { Dialect } from '../core/dialect.js';
+import { LintEngine } from '../core/analysis/lint-engine.js';
+import { createSchemaContext } from '../core/analysis/scope.js';
+import { ActionsBlock } from '../blocks.js';
+import { requiredFieldPass } from './required-fields.js';
+
+const TestSchema = {
+  actions: ActionsBlock,
+};
+
+const schemaCtx = createSchemaContext({ schema: TestSchema, aliases: {} });
+
+function getDiagnostics(source: string, code?: string) {
+  const { rootNode: root } = parse(source);
+  const mappingNode =
+    root.namedChildren.find(n => n.type === 'mapping') ?? root;
+
+  const dialect = new Dialect();
+  const result = dialect.parse(mappingNode, TestSchema);
+
+  const engine = new LintEngine({
+    passes: [requiredFieldPass()],
+    source: 'test',
+  });
+  const { diagnostics } = engine.run(result.value, schemaCtx);
+  if (!code) return diagnostics;
+  return diagnostics.filter(d => d.code === code);
+}
+
+describe('required target on ActionBlock', () => {
+  it('flags an action that has only a description', () => {
+    const diags = getDiagnostics(
+      `
+actions:
+  Notify_Manager:
+    description: "Notify the store manager"
+`,
+      'missing-required-field'
+    );
+    expect(diags).toHaveLength(1);
+    expect(diags[0].message).toContain('target');
+  });
+
+  it('does not flag an action that declares target', () => {
+    const diags = getDiagnostics(
+      `
+actions:
+  Notify_Manager:
+    description: "Notify the store manager"
+    target: "flow://Notify_Manager"
+`,
+      'missing-required-field'
+    );
+    expect(diags).toHaveLength(0);
+  });
+
+  it('flags an action with inputs/outputs but no target', () => {
+    const diags = getDiagnostics(
+      `
+actions:
+  Lookup:
+    description: "Look something up"
+    inputs:
+      query: string
+    outputs:
+      result: string
+`,
+      'missing-required-field'
+    );
+    expect(diags).toHaveLength(1);
+    expect(diags[0].message).toContain('target');
+  });
+
+  it('reports one diagnostic per action when multiple are missing target', () => {
+    const diags = getDiagnostics(
+      `
+actions:
+  Alpha:
+    description: "alpha"
+  Beta:
+    description: "beta"
+    target: "flow://Beta"
+  Gamma:
+    description: "gamma"
+`,
+      'missing-required-field'
+    );
+    expect(diags).toHaveLength(2);
+  });
+});