fix: normalize MCP empty tool schemas (#75401) (thanks @SymbolStar)

CHANGELOG.md

@@ -87,6 +87,7 @@ Docs: https://docs.openclaw.ai
 - Plugins/hooks: derive hook `ctx.channelId` from the conversation target instead of the provider name, so Discord and other channel plugins can keep per-channel state isolated. Fixes #59881. Thanks @bradfreels.
 - Gateway/config: log config health-state write failures instead of silently hiding config observe-recovery write errors. Thanks @sallyom.
 - Diagnostics: reset stuck-session timers on reply, tool, status, block, and ACP progress events, and back off repeated `session.stuck` diagnostics while a session remains unchanged. Supersedes #72010. Thanks @rubencu.
+- Agents/OpenAI: normalize parameter-free MCP tool schemas whose `properties` value is null or undefined, so OpenAI no longer rejects MCP tools without parameters. Fixes #75362. (#75401) Thanks @SymbolStar.
 
 ## 2026.4.30
 

src/agents/pi-tools-parameter-schema.ts

@@ -134,10 +134,6 @@ function isTypedSchemaMissingProperties(
   if (!("type" in schemaRecord) || conditionalKey !== null) {
     return false;
   }
-  // Treat both missing `properties` and `properties` set to a non-object value
-  // (e.g. undefined/null) as "missing properties" — MCP servers sometimes return
-  // `{ type: "object" }` or `{ type: "object", properties: undefined }` for
-  // parameter-free tools.
   if (!("properties" in schemaRecord)) {
     return true;
   }

src/agents/pi-tools.schema.test.ts

@@ -207,6 +207,8 @@ describe("normalizeToolParameters", () => {
     expect(parameters.type).toBe("object");
     expect(parameters.properties).toEqual({});
   });
+
+  it("preserves existing properties on type:object schemas", () => {
     const tool: AnyAgentTool = {
       name: "query",
       label: "query",