More extensible CallToolRequest

Expected Behavior

We want to define our own tool-specific requests with own parsers for 'params'.

Current Behavior

The arguments for tool calls are always Maps.

Context

We develop our own MCP server that offers features like querying and we have our own set of tools to parse, validate and execute them.

The problem is that request object is always de-serialised as a map and we need to serialise it back or figure out a way to reconstruct our objects from the maps. It works most of the time, but is rather inconvenient for queries.

There is https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/json/McpJsonMapper.java, but as far as I understand, it is mainly used to decouple Jackson from the rest of the code.

We could have used that but it looks rather technical.

What I would like to have: some way to define my own request objects and make their payloads shallow or leave them unparsed so the each individual tool can later parse its payload and decide what to do. Or stick with standard map-based one if that is fine for it.

首先阅读 McpJsonMapper.java，并跟踪 CallToolRequest 如何反序列化工具参数。在保留现有基于 map 的行为的同时，定义受支持的工具特定请求解析扩展点，然后通过相关的请求反序列化测试验证所选择的行为。