Resource Handles

Large GeoJSON and CZML payloads should not be repeated through every model tool call. Cesium MCP can store the payload once and pass a compact resourceId to later visualization tools.

GeoJSON / CZML payload
        ↓ storeResource
session-scoped resourceId
        ↓ addGeoJsonLayer / loadCzml / addHeatmap / ...
adapter resolves data
        ↓
unchanged Cesium Bridge action

The resource layer belongs to the MCP or WebMCP adapter. It does not change the browser Bridge protocol and it does not mix transient payloads with Cesium scene state.

MCP runtime

storeResource, listResources, and deleteResource are always available independently of toolset selection:

{
  "name": "storeResource",
  "arguments": {
    "kind": "geojson",
    "data": {
      "type": "FeatureCollection",
      "features": []
    }
  }
}

Use the returned ID instead of repeating data:

{
  "name": "addGeoJsonLayer",
  "arguments": {
    "resourceId": "resource_mabc_1",
    "name": "Boundaries"
  }
}

Runtime stores are isolated by browser sessionId. The same ID is not visible to a different browser session.

WebMCP and function calling

Resource tools are opt-in for existing applications, so the default 15-tool surface remains unchanged:

const registration = await registerCesiumViewerWebMcp(viewer, {
  enableResources: true,
})

const stored = registration.resourceStore!.register({
  kind: 'geojson',
  data: largeFeatureCollection,
})

An application may also provide its own store:

const resourceStore = createCesiumResourceStore()

await registerCesiumViewerWebMcp(viewer, {
  resourceStore,
  toolsets: 'all',
})

The hosted Browser Agent enables these tools and shares one page-local store between native WebMCP and its built-in function-calling agent.

Supported consumers

Resource kind	Tools accepting resourceId
geojson	addGeoJsonLayer, addGeoJsonPrimitive, addLabel, addHeatmap
czml	loadCzml
json	Reserved for application and future analysis tools

Lifecycle and limits

• In-memory and intentionally ephemeral; resources are not scene persistence.
• Default expiry: 30 minutes after registration.
• Default capacity: 100 resources per store.
• Default maximum: 10 MiB per resource.
• listResources returns metadata only, never the stored payload.
• This store is suitable for one Runtime process or one browser page. Multi-instance deployments should provide a shared storage adapter in a future implementation.

Existing data and url inputs remain fully compatible. resourceId is mutually exclusive with both.