Enum MessageMcpResponse 

#[non_exhaustive]
pub enum MessageMcpResponse {
    Result {
        result: Value,
        meta: Option<Map<String, Value>>,
    },
    Error {
        error: McpError,
        meta: Option<Map<String, Value>>,
    },
}

Available on crate features unstable_mcp_over_acp and unstable_protocol_v2 only.

UNSTABLE

The successful outer ACP mcp/message response carries exactly one inner MCP outcome: an opaque result (including JSON null), or an MCP error. Outer ACP errors are reserved for binding and runtime failures.

Both branches require their carrier key. An error must be a non-null object. Unknown outer fields are ignored; inner result and error fields are preserved. Carrier _meta is optional; null or invalid values are treated as absent. Senders must include exactly one outcome; receivers prefer result if both are present.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Result

An opaque inner MCP result.

Fields

result: Value

Required, even if JSON null.

meta: Option<Map<String, Value>>

The _meta property is reserved by ACP to allow clients and agents to attach additional metadata to their interactions. Omitted and null are equivalent and mean no metadata. Implementations MUST NOT make assumptions about values at these keys. This is ACP metadata, not the inner MCP message’s _meta.

See protocol docs: Extensibility

Error

A structured inner MCP error.

Fields

error: McpError

Required, non-null MCP error object.

meta: Option<Map<String, Value>>

The _meta property is reserved by ACP to allow clients and agents to attach additional metadata to their interactions. Omitted and null are equivalent and mean no metadata. Implementations MUST NOT make assumptions about values at these keys. This is ACP metadata, not the inner MCP message’s _meta.

See protocol docs: Extensibility

Implementations

impl MessageMcpResponse

pub fn success(result: Value) -> Self

Wrap any JSON result without interpreting its MCP result type.

pub fn error(error: McpError) -> Self

Wrap an inner MCP error in a successful outer ACP response.

pub fn meta(self, meta: impl IntoOption<Map<String, Value>>) -> Self

Attach optional carrier-level ACP metadata.

Trait Implementations

impl Clone for MessageMcpResponse

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MessageMcpResponse

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for MessageMcpResponse

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for MessageMcpResponse

impl JsonSchema for MessageMcpResponse

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for MessageMcpResponse

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for MessageMcpResponse

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for MessageMcpResponse