JSONPath in checks

Built-in checks like Groundedness, StringMatching, and LessThan accept path parameters such as target_key, context_key, and question_key that point into the trace. This page covers the syntax.

The trace. Prefix

All paths must start with trace.:

# Correct
Groundedness(target_key="trace.last.outputs.answer", ...)

# Wrong — raises an error
Groundedness(target_key="last.outputs.answer", ...)

trace.last

trace.last is shorthand for trace.interactions[-1] — the most recent interaction. Use an explicit index to reference earlier turns in multi-turn scenarios:

target_key = "trace.last.outputs"  # most recent
target_key = "trace.interactions[0].outputs"  # first interaction
target_key = "trace.interactions[-1].outputs"  # same as trace.last.outputs

Common Patterns

Path	What it accesses
trace.last.inputs	Last interaction inputs
trace.last.outputs	Last interaction outputs
trace.last.outputs.answer	Nested field in output dict
trace.last.outputs.confidence	Numeric field in output dict
trace.last.metadata.model	Metadata field
trace.interactions[0].inputs	First interaction inputs

NoMatch

When a path can’t be resolved, the resolver returns a NoMatch sentinel instead of raising an exception. Every built-in check turns NoMatch into CheckResult.error, not a failure, with a message naming the path it could not resolve.

The distinction matters when you read results. A failure means the check ran and your agent did not meet the bar. An error means the check could not run at all, usually because you typed the path wrong or the output shape changed.

Follow the same convention in custom checks:

from giskard.checks.core.extraction import resolve, NoMatch

value = resolve(trace, self.field_path)
if isinstance(value, NoMatch):
    return CheckResult.error(message=f"No value at '{self.field_path}'")

Paths in Jinja2 Templates

LLM-based check prompts use Jinja2. Inside a template, trace is a variable — use the same dot notation without quoting:

User: {{ trace.last.inputs }}
Response: {{ trace.last.outputs }}
Turn 1: {{ trace.interactions[0].outputs }}