Nested schema validation errors are not serialized or logged in a useful way

[dfalling]

When calling my server's tool with nested fields or embed_one's, any validation errors are not properly serialized:

My caller only receives this:

MCP error -32602: Invalid params

My logs show no failures or debug output. I have to override handle_request to debug:

  def handle_request(%{"method" => "tools/call", "params" => %{"name" => name, "arguments" => args}} = req, frame) do
    require Logger

    Logger.info("=== Tool Call: #{name} ===")
    Logger.info("Arguments: #{inspect(args, pretty: true, limit: :infinity)}")

    registered_tools = Hermes.Server.Handlers.get_server_tools(__MODULE__, frame)

    case Enum.find(registered_tools, &(&1.name == name)) do
      nil ->
        Logger.error("Tool not found: #{name}")

      tool ->
        case tool.validate_input.(args) do
          {:ok, _validated} ->
            Logger.info("✓ Validation passed")

          {:error, raw_errors} ->
            Logger.error("✗ RAW Validation errors:")
            Logger.error(inspect(raw_errors, pretty: true, limit: :infinity))
        end
    end

    result = Hermes.Server.Handlers.handle(req, __MODULE__, frame)

    case result do
      {:error, error, _frame} ->
        Logger.error("Tool call failed: #{inspect(error, pretty: true)}")

      _ ->
        Logger.info("Tool call succeeded")
    end

That gets me access (in my logs) to much more useful debug info:

[error] ✗ RAW Validation errors:
[error] [
  %Peri.Error{
    path: [:location],
    key: :location,
    content: nil,
    message: nil,
    errors: [
      %Peri.Error{
        path: [:location, :latitude],
        key: :latitude,
        content: %{actual: "32.5355", expected: :number},
        message: "expected type of :number received 32.5355 value",
        errors: nil
      }
    ]
  },
  %Peri.Error{
    path: [:location],
    key: :location,
    content: nil,
    message: nil,
    errors: [
      %Peri.Error{
        path: [:location, :longitude],
        key: :longitude,
        content: %{actual: "44.4275", expected: :number},
        message: "expected type of :number received 44.4275 value",
        errors: nil
      }
    ]
  }
]

I finally found my specific issue was because :number was being coerced into string, and then erroring. When I changed :number to :float, it worked fine.