Per the MCP spec [1] and the TypeScript schema [2], `CallToolResult.content` is typed as `ContentBlock[]`, so it is a required array with no minimum length constraint. MCP server libraries use such a representation in practice: for example, FastMCP returns responses with no `structuredContent` and an empty `content` array when tools return `None`. [1]: https://modelcontextprotocol.io/specification/2025-11-25/server/tools [2]: https://github.com/modelcontextprotocol/specification/blob/main/schema/2025-11-25/schema.ts |
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| rmcp-macros | ||