responds with

responds with

Declare the output contract for a machine. The responds with section defines what data a machine returns after execution. Each field has a name, type, and optional source mapping. The runtime validates the machine’s output against this contract, and callers can rely on the declared shape.

Replaces the legacy provides > outputs syntax. The parser accepts both forms; run mashin fmt to auto-migrate.

When to use

Every machine that produces output should have a responds with section. Omit it only for fire-and-forget machines (like notification senders) where the caller does not need a return value.

Syntax

responds with
  <field_name> as <type>
  <field_name> as <type>, <modifiers>
  ...

Field declaration

Each field follows the pattern:

<name> as <type>, <modifier1>, <modifier2>, ...

Types

Same types as accepts: text, string, number, integer, decimal, boolean, list, list of <type>, map, any.

Modifiers

Modifier	Description	Example
from <step_name>	Map this output field from a specific step’s output	summary as text, from analyze
from state.<field>	Map from machine state	count as integer, from state.counter
default <value>	Default value if the source field is null	done as boolean, default true

Source mapping with from

The from modifier provides declarative output mapping. Instead of writing a final compute step to assemble the output, you can map output fields directly to step results or state:

responds with
  summary as text, from analyze
  confidence as number, from analyze
  attempt_count as integer, from state.retries, default 0
  completed as boolean, default true

Without from, output fields are populated from the last step’s return value. If the last step returns {summary: "...", confidence: 0.9}, those values map to matching output field names.

Examples

Simple outputs

responds with
  greeting as text
  timestamp as number

With source mapping

machine research_assistant
  accepts
    question as text, is required

  responds with
    answer as text, from search
    sources as list, from search
    cached as boolean, from state.was_cached, default false

  implements
    state
      was_cached: boolean, default: false

    ask search, using: "anthropic:claude-sonnet-4-6"
      with task "Research this question: ${input.question}"
      returns
        answer as text
        sources as list
      assuming
        answer: "Based on research..."
        sources: ["source1.com"]

Typed lists

responds with
  items as list of text
  scores as list of number
  results as list of map

Full machine with responds with

machine sentiment_classifier
  accepts
    text as text, is required

  responds with
    sentiment as text
    confidence as number
    keywords as list of text

  implements
    ask classify, using: "anthropic:claude-haiku-4"
      with task "Classify the sentiment and extract keywords.\n\nText: ${input.text}"
      returns
        sentiment as text
        confidence as number
        keywords as list of text
      assuming
        sentiment: "positive"
        confidence: 0.92
        keywords: ["great", "excellent"]

Output validation

The runtime validates that the machine’s final output matches the responds with contract:

• All declared fields must be present in the output (unless they have a default)
• Field types are checked at runtime
• Extra fields not declared in responds with are stripped from the output

If validation fails, the machine returns an error rather than invalid output. This protects callers from receiving unexpected data shapes.

Governance

Output validation is recorded in the behavioral ledger. If the output contract is violated (missing field, wrong type), the violation is recorded as a step event. This makes output contract violations auditable.

The responds with section itself has no governance cost. It is a compile-time declaration that the runtime uses for validation.

Translations

Language	Keyword
English	responds with
Spanish	responde con
French	repond avec
German	antwortet mit
Japanese	で応答する
Chinese	回应返回
Korean	로 응답한다

See also

• accepts - Input contract declaration
• implements - Where steps produce output values
• verifies - Test cases that assert output via expect
• achieves - Goal examples with expected outputs