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Testing & evals
Extractors
Built-in Extractors
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Built-in Extractors

Letta Evals provides a set of built-in extractors that cover the most common extraction needs.

Common Extractors

Section titled “Common Extractors”

last_assistant

Section titled “last_assistant”

Extracts the last assistant message content.

extractor: last_assistant # Most common - gets final response

first_assistant

Section titled “first_assistant”

Extracts the first assistant message content.

extractor: first_assistant

all_assistant

Section titled “all_assistant”

Concatenates all assistant messages with a separator.

extractor: all_assistant
extractor_config:
  separator: "\n\n" # Join messages with double newline

pattern

Section titled “pattern”

Extracts content matching a regex pattern.

extractor: pattern
extractor_config:
  pattern: 'Result: (\d+)' # Regex pattern to match
  group: 1 # Extract capture group 1

tool_arguments

Section titled “tool_arguments”

Extracts arguments from a specific tool call.

extractor: tool_arguments
extractor_config:
  tool_name: search # Which tool to extract from

tool_output

Section titled “tool_output”

Extracts the return value from a specific tool call.

extractor: tool_output
extractor_config:
  tool_name: search

memory_block

Section titled “memory_block”

Extracts content from a specific memory block.

extractor: memory_block
extractor_config:
  block_label: human # Which memory block to extract

after_marker

Section titled “after_marker”

Extracts content after a specific marker string.

extractor: after_marker
extractor_config:
  marker: "ANSWER:"
  include_marker: false

Next Steps

Section titled “Next Steps”