Struct LogMessageParams 

#[non_exhaustive]
pub struct LogMessageParams {
    pub level: LoggingLevel,
    pub logger: Option<String>,
    pub message: String,
    pub data: Option<Value>,
}

Log message notification.

The wire contract pmcp emits

The MCP schema declares LoggingMessageNotificationParams as { level, logger?, data } — data is REQUIRED and there is no message member at all (schema/vendored/core-2026-07-28/schema.ts). This Rust type is the reverse shape: a required message and an optional data. The two are reconciled at the EMITTER, not here: RequestHandlerExtra::log defaults data to the message string when the caller supplied none, so every frame pmcp emits carries data, and message rides alongside it as a pmcp extension. When the caller used log_with_data, their value is passed through verbatim.

The reason, so this is not “simplified” back: the official reference client’s LoggingMessageNotificationParamsSchema uses z.unknown(), which is non-optional under the bundled zod v4. A frame with no data fails to parse (invalid_type at params.data: expected nonoptional, received undefined) and the client drops it silently — measured against the pinned conformance suite, where it cost 2025-11-25:tools-call-with-logging its score and tripped the suite’s WireSchemaValid check with LoggingMessageNotification/params: must have required property 'data'.

Keeping message is legal: the schema does not close additionalProperties, and the reference client strips unknown members rather than rejecting them. It is also what keeps this a non-breaking fix — removing message would be a breaking change to a public type, and was rejected in favour of defaulting data.

Constructing this type directly (rather than through the emitter) does NOT get the default: new leaves data as None, so a caller building the params by hand should call with_data.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

level: LoggingLevel

Log level

logger: Option<String>

Logger name/category

message: String

Log message

data: Option<Value>

Additional data

Implementations

impl LogMessageParams

pub fn new(level: LoggingLevel, message: impl Into<String>) -> Self

Create a log message with level and message.

logger and data default to None.

pub fn with_logger(self, logger: impl Into<String>) -> Self

Set the logger name/category.

pub fn with_data(self, data: Value) -> Self

Set additional data.

Trait Implementations

impl Clone for LogMessageParams

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 LogMessageParams

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for LogMessageParams

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for LogMessageParams

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

where __S: Serializer,

Serialize this value into the given Serde serializer.