MCP-only agents

An agent can be nothing but an MCP server. Build the server and the agent comes with it: no context provider, and nothing in the server needs to know about newt.

[agents.tasks]
mcp = "https://app.example.com/tasks/mcp"
model = "default"
token_env = "TASKS_TOKEN"

newt sends the agent’s token to the server as the bearer.

What newt takes from the server

The agent’s	Comes from
Instructions	The server’s instructions. Empty instructions fail the turn.
Model	model in server.toml
Tools	tools/list
Skills	skills/list, named {agent}/{skill path} (experimental)
Workspace pages	The session’s resources, loaded at the start of each turn

There is no version, pinned, turn instructions or constraints. newt reconnects when the tool set goes stale, which includes the server restarting.

Resources are the workspace

At the start of each turn newt lists and reads the resources with _meta: { "newt/session": "<key>" }, so one server can serve every session. Each text resource becomes a page:

Page field	From the resource
path	name
key	_meta["newt/key"] when set, otherwise [uri]
version	The sha256: digest of the text
content	The text contents

Keeping pages fresh

newt subscribes to the session’s resources for the rest of the turn. notifications/resources/updated marks one page stale and notifications/resources/list_changed marks them all; the next read fetches again.

Tip

The update notification travels on its own stream, so it can arrive after the tool result that caused it. A tool that changes a page should also return newt/invalidate, or the page itself in newt/pages, so the model’s next read sees the change for certain.

Next

• assistant-mcp in crates/newt-demo is a complete example. Run it with the Quickstart.
• Protocol 2.7 has every rule.