Struct ClientCapabilities 

pub struct ClientCapabilities {
    pub roots: Option<RootsCapabilities>,
    pub sampling: Option<SamplingCapabilities>,
    pub elicitation: Option<ElicitationCapabilities>,
    pub experimental: Option<HashMap<String, Value>>,
    pub extensions: Option<HashMap<String, Value>>,
}

Capabilities that a client may support.

2026-07-28 shape:

• experimental?: { [k]: JSONObject }
• roots?: {} — presence means client supports listing roots
• sampling?: { context?, tools? }
• elicitation?: { form?, url? }
• extensions?: { [k]: JSONObject } — reverse-DNS keyed extension capability map

Note: tasks field is NOT present — tasks moved entirely to extension in 2026-07-28 (SEP-2663). Advertise tasks support via extensions["io.modelcontextprotocol/tasks"].

Fields

roots: Option<RootsCapabilities>

Root directory capabilities. Deprecated per SEP-2577.

sampling: Option<SamplingCapabilities>

Sampling capabilities (client can handle sampling requests from server). Deprecated per SEP-2577.

elicitation: Option<ElicitationCapabilities>

Elicitation capabilities (client can handle elicitation requests from server).

experimental: Option<HashMap<String, Value>>

Experimental capabilities.

extensions: Option<HashMap<String, Value>>

MCP extensions the client supports. Keys are reverse-DNS extension identifiers (e.g. "io.modelcontextprotocol/oauth-client-credentials"); values are per-extension settings. Empty {} means support without settings.

Trait Implementations

impl Clone for ClientCapabilities

fn clone(&self) -> ClientCapabilities

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ClientCapabilities

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

Formats the value using the given formatter.

impl Default for ClientCapabilities

fn default() -> ClientCapabilities

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for ClientCapabilities

fn deserialize<__D>( __deserializer: __D, ) -> Result<ClientCapabilities, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for ClientCapabilities

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.