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Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
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Your Question

How can I access the _meta information present in the CallToolRequest and use it within the tool execution logic?
I need to send tokens through the _meta field and consume them during tool execution.

Currently, I'm using:

tool.call().apply(exchange, callToolRequest.arguments())

However, it seems that the full request (including _meta) isn't being passed through. Is there a way to retrieve the complete request, including the metadata?

private McpServerSession.RequestHandler toolsCallRequestHandler() {
return (exchange, params) -> {
McpSchema.CallToolRequest callToolRequest = objectMapper.convertValue(params,
new TypeReference<McpSchema.CallToolRequest>() {
});

		Optional<McpServerFeatures.AsyncToolSpecification> toolSpecification = this.tools.stream()
			.filter(tr -> callToolRequest.name().equals(tr.tool().name()))
			.findAny();
		if (toolSpecification.isEmpty()) {
			return Mono.error(new McpError("Tool not found: " + callToolRequest.name()));
		}
		return toolSpecification.map(tool -> tool.call().apply(exchange, callToolRequest.arguments()))
			.orElse(Mono.error(new McpError("Tool not found: " + callToolRequest.name())));
	};
}