mcp_tool

The mcp_tool attribute macro generates a Tool from your struct with rich metadata.

#[macros::mcp_tool(
    name = "write_file",
    title = "Write File Tool",
    description = "Create or overwrite a file with new content.",
    destructive_hint = false,
    idempotent_hint = false,
    open_world_hint = false,
    read_only_hint = false,
    meta = r#"{ "version": "1.0" }"#,
    execution(task_support = "optional"),
    icons = [(
        src = "https://example.com/write.png",
        mime_type = "image/png",
        sizes = ["128x128"],
        theme = "light"
    )]
)]
#[derive(Debug, serde::Deserialize, serde::Serialize, macros::JsonSchema)]
pub struct WriteFileTool {
    /// The target file path
    pub path: String,
    /// The content to write
    pub content: String,
}

This generates:

• WriteFileTool::tool() - returns a Tool instance
• WriteFileTool::tool_name() - returns "write_file"
• JSON Schema for the struct fields

Execution Hints

Attribute	Description
task_support = "forbidden"	Tool must not use tasks
task_support = "required"	Tool must use tasks
task_support = "optional"	Tool may use tasks
(omitted)	No task support

Destructiveness Hints

• destructive_hint - the tool modifies data
• idempotent_hint - calling multiple times has same effect
• open_world_hint - output depends on external state
• read_only_hint - the tool only reads data