Varin

{
  "schemaVersion": 1,
  "id": "example.agent-authored-panel",
  "version": "1.0.0",
  "engines": { "varin": "*" },
  "entrypoints": {
    "host": { "file": "host.js", "mode": "brokered",
              "activation": ["service-request"] },
    "surfaces": [{ "id": "panel", "file": "surface.cjs", "mode": "managed",
      "supports": ["web", "desktop"], "activation": ["application-startup"] }]
  },
  "provides": { "services": [{
    "id": "example.agent-authored-panel.count", "version": 1,
    "tool": { "name": "authored_text_count", "completion": "result",
              "operation": "read", "inputSchema": { … } }
  }] },
  "contributions": [{
    "id": "example.agent-authored-panel.summary", "kind": "panel",
    "entrypoint": "panel", "supports": ["web", "desktop"],
    "placement": { "slot": "workbench.secondary.after", "order": 20 }
  }]
}

import { defineHostExtension, provideTool } from '@varin/extension-sdk';
import manifest from './varin.extension.json' with { type: 'json' };
 
export default defineHostExtension({
  activate(context) {
    // The same service the manifest declares: discovery and activation read one description
    provideTool(context, manifest.provides.services[0], async (input, call) => {
      // Call a built-in tool from the new one; the original receipt is kept intact
      const memory = await call.tools.invoke({
        callId: 'memory', name: 'memory', arguments: input.memory,
      });
      return { memory };
    });
  },
});

Manifest excerpted from examples/extensions/agent-authored-panel with long schemas elided; host.ts simplified from nested-tools.