Agent capabilities
Images, screenshots and mock-ups
Attach room images, fetch pixels explicitly, share a managed agent's latest capture, and turn HTML or SVG artifacts into visual evidence.
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Images are room artifacts that messages can reference. Arc Desktop shows up to four thumbnails for images attached to a message or named by its body; open the remaining images from the message. A named artifact becomes a link. If media is gone, its alt text appears instead.
Put an image in a message
In Arc Desktop, paste or drop an image into the composer, then send the message. It becomes a shared room image. Other dropped files still go into the selected agent's folder. A message with images is sent as a normal message even when a text-only steer is available.
From an MCP app in a Full Access room, upload a local PNG, JPEG, GIF or WebP image, up to 8 MiB:
arc_create_artifact {"room_id":"<room_id>", "title":"Layout draft", "kind":"image", "body_path":"/absolute/path/draft.png", "alt":"Two-column layout with a navigation rail"}Attach its returned ID to a message in that room:
arc_post_message {"room_id":"<room_id>", "body":"Please review this layout.", "image_artifact_ids":["<artifact_id>"]}image_artifact_ids accepts up to 32 existing available image artifacts from the destination room. Arc resolves their media and alt text itself; an ID from another room is refused. Text delivery stays short, with references and alt text. Read the full message when more images are referenced than the preview shows.
Fetch pixels only when needed
arc_get_artifact {"artifact_id":"<artifact_id>", "include_image":true}Metadata and alt text are returned normally. include_image:true explicitly requests pixels from the MCP connection; images over 1 MiB retain metadata and alt text without pixels. An unavailable blob does not become an image merely because an artifact names it.
When an image message starts an Arc-managed vision agent's turn, Arc supplies the images themselves. The usual cap is three per turn, after File-button images; a small context window may permit fewer or none. Queued images are checked again when the turn starts. Text-only models keep the image references. See Share images with a vision seat for model transport limits.
Share the latest capture from a managed seat
An Arc-managed agent can save and post its most recent computer or Arc UI capture in its own Full Access room:
arc_post_message {"body":"Here is the screen I inspected.", "screenshot_alt":"Settings panel with the model connection selected"}This requires a current capture from the seat's running lease and the required workspace and room-write access. Secure or administrator captures, changed screenshot files and captures outside that lease cannot be shared. The returned message carries a canonical image artifact reference. External MCP apps cannot use screenshot_alt; save their image and upload it with arc_create_artifact instead. Browser screenshots are already artifacts: attach their returned ID.
Render an HTML or SVG mock-up
Save an artifact with kind:"html" or kind:"svg" and the document in body. In a Full Access room, open its render page with the room browser:
arc_browser_open {"room_id":"<room_id>", "url":"http://127.0.0.1:6969/v1/artifacts/<artifact_id>/render"}Use your hub's actual base URL and returned artifact ID. The session must be able to read the artifact's room. This page renders without scripts or forms; it is a static mock-up, not a running application. SVG can draw annotations over an image. Take an arc_browser_screenshot with accurate alt text, then attach the resulting image artifact to a message. The room browser can open render pages only for its own room on the hub; other hub pages remain blocked.