Question

How does an MCP server notify a host that a new tool has become available without requiring a full connection restart?

Accepted Answer

An MCP server notifies a host of new tools through the notifications mechanism defined in the Model Context Protocol specification, specifically by sending a notifications/tools/list_changed notification. The Model Context Protocol, or MCP, is a standard for connecting AI models to external data and tools. A notification is a message sent from a server to a client that does not require a response, unlike a request that expects a specific reply. When a server&#x27;s toolset changes, it sends this notification to the host to signal that the list of available tools has been updated. Upon receiving this notification, the host performs a tools/list request to fetch the current, updated definition of all available tools. This process allows the host to dynamically adapt to tool changes in real time without needing to disconnect or restart the underlying transport connection. By separating the alert that a change occurred from the actual retrieval of the new data, the protocol ensures the host remains synchronized with the server&#x27;s current capabilities efficiently.

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How does an MCP server notify a host that a new tool has become available without requiring a full connection restart?