[MCP Bundle] Allow for is_error control on tool call return

[EdouardCourty]

Hi, currently tool calling supports returning dependents of Content, strings and arrays.
However, it is not possible to control the value of the is_error key.

I suggest implementing a way to control this value, maybe by either :

• Throwing a specific exception (like ToolErrorException which would be caught in special way
• Forcing the tools to return an instance of Content or a ToolResult class that could contain an array of contents, and a is_error boolean

I personally think the second option is best, since it would standardise the way tool calls are done.
That's what I had done in my own implementation of MCP here : https://github.com/EdouardCourty/mcp-server-bundle/blob/main/src/DependencyInjection/CompilerPass/ToolPass.php#L90, and it worked really well!

[chr-hertel]

I think this is most likely rather about the SDK itself, right?

We merged modelcontextprotocol/php-sdk#93 today, does that help with your case?

[EdouardCourty]

I think this is most likely rather about the SDK itself, right?

We merged modelcontextprotocol/php-sdk#93 today, does that help with your case?

Sorry, I was reading the source code in my IDE and didn't think about the SDK's repo !

This actually serves my point, thank your for your time!