Struct Observation 

pub struct Observation {

    pub id: Id,
    pub trace_id: Id,
    pub parent_observation_id: Option<Id>,
    pub name: String,
    pub observation_type: ObservationType,
    pub start_time: DateTime<Utc>,
    pub end_time: Option<DateTime<Utc>>,
    pub input: Option<Value>,
    pub output: Option<Value>,
    pub metadata: Value,
    pub level: ObservationLevel,
    pub status_message: Option<String>,
    pub model: Option<String>,
    pub model_parameters: Option<Value>,
    pub usage: Option<TokenUsage>,
    pub cost: Option<f64>,
}

Observation represents a single unit of work within a trace.

Observations form a tree structure via parent_observation_id. A graph invocation creates observations for each superstep, node execution, LLM call, and tool call.

Fields

id: Id

Unique observation identifier.

trace_id: Id

Parent trace identifier.

parent_observation_id: Option<Id>

Parent observation identifier for nesting (None = top-level).

name: String

Human-readable name (node name, model name, tool name).

observation_type: ObservationType

Type of observation.

start_time: DateTime<Utc>

Observation start timestamp.

end_time: Option<DateTime<Utc>>

Observation end timestamp.

input: Option<Value>

Input data (prompt messages, tool arguments, etc.).

output: Option<Value>

Output data (completion text, tool result, etc.).

metadata: Value

Arbitrary key-value metadata.

level: ObservationLevel

Severity level.

status_message: Option<String>

Human-readable status message (error details, etc.).

model: Option<String>

LLM model name (e.g., “claude-sonnet-4-20250514”).

model_parameters: Option<Value>

Model parameters (temperature, max_tokens, etc.).

usage: Option<TokenUsage>

Token usage statistics.

cost: Option<f64>

Cost in USD for this call.

Implementations

impl Observation

pub fn span(trace_id: Id, name: impl Into<String>) -> Self

Create a new span observation.

pub fn generation( trace_id: Id, name: impl Into<String>, model: impl Into<String>, ) -> Self

Create a new LLM generation observation.

pub fn tool_call(trace_id: Id, name: impl Into<String>) -> Self

Create a new tool call observation.

pub const fn with_parent(self, parent_id: Id) -> Self

Set the parent observation for nesting.

pub fn complete(&mut self, output: Option<Value>)

Mark the observation as completed with optional output.

pub fn fail(&mut self, message: impl Into<String>)

Mark the observation as failed with an error message.

pub fn duration_ms(&self) -> Option<u64>

Duration in milliseconds (if completed).

Trait Implementations

impl Clone for Observation

fn clone(&self) -> Observation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Observation

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Observation

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Observation

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

where __S: Serializer,

Serialize this value into the given Serde serializer.