Trait ResourceHandler 

pub trait ResourceHandler: Send + Sync {
    // Required methods
    fn definition(&self) -> Resource;
    fn read(&self, ctx: &McpContext) -> McpResult<Vec<ResourceContent>>;

    // Provided methods
    fn template(&self) -> Option<ResourceTemplate> { ... }
    fn icon(&self) -> Option<&Icon> { ... }
    fn version(&self) -> Option<&str> { ... }
    fn tags(&self) -> &[String] { ... }
    fn timeout(&self) -> Option<Duration> { ... }
    fn read_with_uri(
        &self,
        ctx: &McpContext,
        _uri: &str,
        _params: &HashMap<String, String>,
    ) -> McpResult<Vec<ResourceContent>> { ... }
    fn read_async_with_uri<'a>(
        &'a self,
        ctx: &'a McpContext,
        uri: &'a str,
        params: &'a HashMap<String, String>,
    ) -> BoxFuture<'a, McpOutcome<Vec<ResourceContent>>> { ... }
    fn read_async<'a>(
        &'a self,
        ctx: &'a McpContext,
    ) -> BoxFuture<'a, McpOutcome<Vec<ResourceContent>>> { ... }
}

Handler for a resource.

This trait is typically implemented via the #[resource] macro.

Sync vs Async

By default, implement read() for synchronous execution. For async resources, override read_async() instead. The router uses read_async_with_uri() so implementations can access matched URI parameters when needed. which defaults to running read() in an async block.

Return Type

Async handlers return McpOutcome<Vec<ResourceContent>>, a 4-valued type.

Required Methods

fn definition(&self) -> Resource

Returns the resource definition.

fn read(&self, ctx: &McpContext) -> McpResult<Vec<ResourceContent>>

Reads the resource content synchronously.

This is the default implementation point. Override this for simple synchronous resources. Returns McpResult which is converted to McpOutcome by the async wrapper.

Provided Methods

fn template(&self) -> Option<ResourceTemplate>

Returns the resource template definition, if this resource uses a URI template.

fn icon(&self) -> Option<&Icon>

Returns the resource’s icon, if any.

Default implementation returns None. Override to provide an icon. Note: Icons can also be set directly in definition().

fn version(&self) -> Option<&str>

Returns the resource’s version, if any.

Default implementation returns None. Override to provide a version. Note: Version can also be set directly in definition().

fn tags(&self) -> &[String]

Returns the resource’s tags for filtering and organization.

Default implementation returns an empty slice. Override to provide tags. Note: Tags can also be set directly in definition().

fn timeout(&self) -> Option<Duration>

Returns the resource’s custom timeout duration.

Default implementation returns None, meaning the server’s default timeout applies. Override to specify a per-handler timeout.

fn read_with_uri( &self, ctx: &McpContext, _uri: &str, _params: &HashMap<String, String>, ) -> McpResult<Vec<ResourceContent>>

Reads the resource content synchronously with the matched URI and parameters.

Default implementation ignores URI params and delegates to read().

fn read_async_with_uri<'a>( &'a self, ctx: &'a McpContext, uri: &'a str, params: &'a HashMap<String, String>, ) -> BoxFuture<'a, McpOutcome<Vec<ResourceContent>>>

Reads the resource content asynchronously with the matched URI and parameters.

Default implementation delegates to the sync read_with_uri() method.

fn read_async<'a>( &'a self, ctx: &'a McpContext, ) -> BoxFuture<'a, McpOutcome<Vec<ResourceContent>>>

Reads the resource content asynchronously.

Override this for resources that need true async execution (e.g., file I/O, database queries, remote fetches).

Returns McpOutcome to properly represent all four states.

The default implementation delegates to the sync read() method.

Implementors