Struct ClientCapabilities 

pub struct ClientCapabilities {
    pub elicitation: Option<ClientElicitation>,
    pub experimental: Option<BTreeMap<String, JsonObject>>,
    pub extensions: Option<BTreeMap<String, JsonObject>>,
    pub roots: Option<Map<String, Value>>,
    pub sampling: Option<ClientSampling>,
}

Latest MCP Protocol 2026_07_28 Capabilities a client may support. Known capabilities are defined here, in this schema, but this is not a closed set: any client can define its own, additional capabilities.

JSON schema

{
 "description": "Capabilities a client may support. Known capabilities are defined here, in this schema, but this is not a closed set: any client can define its own, additional capabilities.",
 "type": "object",
 "properties": {
   "elicitation": {
     "description": "Present if the client supports elicitation from the server.",
     "type": "object",
     "properties": {
       "form": {
         "$ref": "#/$defs/JSONObject"
       },
       "url": {
         "$ref": "#/$defs/JSONObject"
       }
     }
   },
   "experimental": {
     "description": "Experimental, non-standard capabilities that the client supports.",
     "type": "object",
     "additionalProperties": {
       "$ref": "#/$defs/JSONObject"
     }
   },
   "extensions": {
     "description": "Optional MCP extensions that the client supports. Keys are extension identifiers\n(e.g., \"io.modelcontextprotocol/oauth-client-credentials\"), and values are\nper-extension settings objects. An empty object indicates support with no settings.\n\nKeys MUST follow the {@link MetaObject_meta key naming rules}, with a\nmandatory prefix.",
     "type": "object",
     "additionalProperties": {
       "$ref": "#/$defs/JSONObject"
     }
   },
   "roots": {
     "description": "Present if the client supports listing roots.",
     "type": "object"
   },
   "sampling": {
     "description": "Present if the client supports sampling from an LLM.",
     "type": "object",
     "properties": {
       "context": {
         "description": "Whether the client supports context inclusion via includeContext parameter.\nIf not declared, servers SHOULD only use includeContext: \"none\" (or omit it).",
         "$ref": "#/$defs/JSONObject"
       },
       "tools": {
         "description": "Whether the client supports tool use via tools and toolChoice parameters.",
         "$ref": "#/$defs/JSONObject"
       }
     }
   }
 }
}

Fields

elicitation: Option<ClientElicitation>

experimental: Option<BTreeMap<String, JsonObject>>

Experimental, non-standard capabilities that the client supports.

extensions: Option<BTreeMap<String, JsonObject>>

Optional MCP extensions that the client supports. Keys are extension identifiers (e.g., “io.modelcontextprotocol/oauth-client-credentials”), and values are per-extension settings objects. An empty object indicates support with no settings. Keys MUST follow the {@link MetaObject_meta key naming rules}, with a mandatory prefix.

roots: Option<Map<String, Value>>

Present if the client supports listing roots.

sampling: Option<ClientSampling>

Implementations

impl ClientCapabilities

pub fn can_handle_request( &self, server_jsonrpc_request: &ServerJsonrpcRequest, ) -> Result<(), RpcError>

Asserts that the client supports the requested server-initiated operation.

In the 2026-07-28 protocol, server→client requests arrive as InputRequests (mid-request) or standalone JSON-RPC requests. Each maps to a client capability:

• sampling/createMessage → sampling
• roots/list → roots
• elicitation/create → elicitation

pub fn can_accept_notification( &self, _notification_method: &str, ) -> Result<(), RpcError>

Asserts that the client can emit the given notification.

Client→server notifications (notifications/cancelled, notifications/progress) are not gated by any client capability, so this always succeeds.

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

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<Self, __D::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::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.