Method render

src/mcp/server/mcpserver/prompts/base.py:138–189

Render the prompt with arguments. Raises: ValueError: If required arguments are missing, or if rendering fails.

(
        self,
        arguments: dict[str, Any] | None,
        context: Context[LifespanContextT, RequestT],
    )

        )

    async def render(
        self,
        arguments: dict[str, Any] | None,
        context: Context[LifespanContextT, RequestT],
    ) -> list[Message]:
        """Render the prompt with arguments.

        Raises:
            ValueError: If required arguments are missing, or if rendering fails.
        """
        # Validate required arguments
        if self.arguments:
            required = {arg.name for arg in self.arguments if arg.required}
            provided = set(arguments or {})
            missing = required - provided
            if missing:
                raise ValueError(f"Missing required arguments: {missing}")

        try:
            # Add context to arguments if needed
            call_args = inject_context(self.fn, arguments or {}, context, self.context_kwarg)

            fn = self.fn
            if is_async_callable(fn):
                result = await fn(**call_args)
            else:
                result = await anyio.to_thread.run_sync(functools.partial(self.fn, **call_args))

            # Validate messages
            if not isinstance(result, list | tuple):
                result = [result]

            # Convert result to messages
            messages: list[Message] = []
            for msg in result:  # type: ignore[reportUnknownVariableType]
                try:
                    if isinstance(msg, Message):
                        messages.append(msg)
                    elif isinstance(msg, dict):
                        messages.append(message_validator.validate_python(msg))
                    elif isinstance(msg, str):
                        content = TextContent(type="text", text=msg)
                        messages.append(UserMessage(content=content))
                    else:  # pragma: no cover
                        content = pydantic_core.to_json(msg, fallback=str, indent=2).decode()
                        messages.append(Message(role="user", content=content))
                except Exception:  # pragma: no cover
                    raise ValueError(f"Could not convert prompt result to message: {msg}")

            return messages
        except Exception as e:
            raise ValueError(f"Error rendering prompt {self.name}: {e}")