MCP Tool description from external source

[askids]

Hi,

Currently, when we define McpServerTool methods under McpServerToolType class, the description corresponding to that particular tool, along with any custom instructions needs to be coded as part of the statically compiled code. However, I want to know, if the tool description can be loaded via an external configuration so that I have ability to update the description, by just publishing an updated configuration instead of needing to publish a new version of the MCP application? My intent is to load this during startup OR as part of periodic config refresh. So the tool request and response will still remain unchanged. Only the instructions on how to use the tool will get updated externally.

Thanks!

[jayaraman-venkatesan]

@askids

If external sources you mean injecting descriptions from configurations on runtime?

Then I would suggest switching from attribute-based registration (WithTools<T>()) to programmatic tool creation using McpServerTool.Create(MethodInfo, McpServerToolCreateOptions).

If you load the configurations from appsettings using IOptionsMonitor<> that should take care of monitoring the changes in configuration and auto updating the description of the tool.

There is also a similar discussion about even adding a tool on runtime here - Discussion-669