Additional parameters are not passed through to tools

Describe the bug
When you pass properties in the arguments of a tools/call message that are not defined in the schema, these are silently dropped from the args object.

To Reproduce

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";

const echoServer = new McpServer({
  name: "Echo",
  version: "1.0.0",
});

const schema = {
  message: z.string().describe("the message to echo"),
};

echoServer.tool("echo", "Echos the input message back", schema, async (args) => {
  console.log({ args });
  return { content: [{ type: "text", text: `Echo: ${props.message}` }] };
});

Call the echo tool with e.g.

{
  "method": "tools/call",
  "params": {
    "name": "echo",
    "arguments": {
      "message": "bar"
      "other": "foo"
    },
    "_meta": {
      "progressToken": 0
    }
  }
}

args will be { message: "bar" }

Expected behavior
It should be possible to pass additional properties to the tool.
This is the JSON Schema generated on the server, by default additionalProperties is set to true.

{
  "tools": [
    {
      "name": "echo",
      "description": "Echos the input message back",
      "inputSchema": {
        "type": "object",
        "properties": {
          "message": {
            "type": "string",
            "description": "the message to echo"
          }
        },
        "required": [
          "message"
        ],
        "additionalProperties": true,
        "$schema": "http://json-schema.org/draft-07/schema#"
      }
    }
  ]
}

Start with the TypeScript SDK path handling the tools/call request and inspect how the tool schema parses its arguments. Reproduce the example with message and other, then verify that the resulting args object preserves the additional property while schema validation still works.