Agents: add skill API rate-limit guardrail (#38452)

* Agents: add rate-limit guardrail for skill API writes

* Changelog: note skill API rate-limit awareness

src/agents/system-prompt.test.ts

@@ -144,6 +144,9 @@ describe("buildAgentSystemPrompt", () => {
 
     expect(prompt).toContain("## Skills (mandatory)");
     expect(prompt).toContain("<available_skills>");
+    expect(prompt).toContain(
+      "When a skill drives external API writes, assume rate limits: prefer fewer larger writes, avoid tight one-item loops, serialize bursts when possible, and respect 429/Retry-After.",
+    );
   });
 
   it("omits skills in minimal prompt mode when skillsPrompt is absent", () => {

src/agents/system-prompt.ts

@@ -29,6 +29,7 @@ function buildSkillsSection(params: { skillsPrompt?: string; readToolName: strin
     "- If multiple could apply: choose the most specific one, then read/follow it.",
     "- If none clearly apply: do not read any SKILL.md.",
     "Constraints: never read more than one skill up front; only read after selecting.",
+    "- When a skill drives external API writes, assume rate limits: prefer fewer larger writes, avoid tight one-item loops, serialize bursts when possible, and respect 429/Retry-After.",
     trimmed,
     "",
   ];