Struct ToolAnnotationsMap 

pub struct ToolAnnotationsMap { /* private fields */ }

A map of tool names to their annotations, for use by middleware.

This is automatically inserted into RouterRequest::extensions for tools/call requests, allowing middleware to inspect tool safety hints (e.g., read_only_hint, destructive_hint) without needing direct access to the router’s tool registry.

Example

use tower_mcp::router::ToolAnnotationsMap;
use tower_mcp::protocol::McpRequest;

// In a middleware Service::call():
fn call(&mut self, req: RouterRequest) -> Self::Future {
    if let McpRequest::CallTool(params) = &req.inner {
        if let Some(map) = req.extensions.get::<ToolAnnotationsMap>() {
            let annotations = map.get(&params.name);
            // Check annotations.read_only_hint, destructive_hint, etc.
        }
    }
    self.inner.call(req)
}

Implementations

impl ToolAnnotationsMap

pub fn get(&self, tool_name: &str) -> Option<&ToolAnnotations>

Look up annotations for a tool by name.

Returns None if the tool has no annotations or doesn’t exist.

pub fn is_read_only(&self, tool_name: &str) -> bool

Check if a tool is read-only (does not modify state).

Returns false if the tool has no annotations or doesn’t exist (the MCP spec default for readOnlyHint is false).

pub fn is_destructive(&self, tool_name: &str) -> bool

Check if a tool may have destructive effects.

Returns true if the tool has no annotations or doesn’t exist (the MCP spec default for destructiveHint is true).

pub fn is_idempotent(&self, tool_name: &str) -> bool

Check if a tool is idempotent.

Returns false if the tool has no annotations or doesn’t exist (the MCP spec default for idempotentHint is false).

Trait Implementations

impl Clone for ToolAnnotationsMap

fn clone(&self) -> ToolAnnotationsMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ToolAnnotationsMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.