blocks.view displays a published Chatblocks code block inside an MCP Apps-compatible chat client. Connect your workspace using the agent setup guide, then ask your agent to list your published blocks and show one with blocks.view.
The tool accepts the block’s opaque id from blocks.list. It is read-only, available on every signed-in plan, and only reads blocks owned by that API key’s workspace. Anonymous playground keys do not expose this tool yet.
Supported blocks
This first version supports self-contained native code blocks: HTML, CSS, JavaScript, and bundled assets, including interactive 3D scenes. Publish the block before displaying it. External network access, third-party script imports, nested websites, stores, live-data widgets, workers, and code requiring dynamic evaluation are not supported in this view. Blocks that declare external network access or a platform-managed format return an explanation instead. Undeclared dependencies can still fail at runtime; this viewer is not an automatic compatibility test. The block runs in a separate sandbox without access to the host’s MCP tools, cookies, storage, forms, popups, or parent page. The host may impose additional restrictions.Client support
Clients without MCP Apps support receive a text response identifying the block and published version, with a link to the Chatblocks workspace. Support depends on the host, not on whether its MCP connection works. The provider implements the stable MCP Apps specification:blocks.view advertises _meta.ui.resourceUri, and the host fetches the HTML through authenticated resources/read. No API key is put in the HTML or a public URL.
This integration is separate from X Player Cards. It does not change X embedding or certify a website’s runtime compatibility.
Plugin packaging
OpenAI’s current plugin architecture can package skills, an MCP connection, and optional MCP Apps UI together for ChatGPT and Codex. A Chatblocks plugin could make installation easier while keeping the same server. Chatblocks currently authenticates MCP requests withcb_live_* API keys; OpenAI’s authenticated plugin flow expects MCP OAuth 2.1. OAuth onboarding and directory packaging are follow-up work, not shipped by this UI provider.
Public submission has separate UI and nested-frame review requirements. This viewer uses an opaque srcdoc child for isolation, declares no remote frameDomains, and has only been exercised in a local SDK host. Actual ChatGPT/Codex support and directory acceptance still require host-specific testing and review. Do not treat a working MCP connection or this local harness as approval for public distribution.