Adding an Attribute

Audience: Pulse internals contributors adding a new ATTR_* operator — a per-record derived value computed from one or more cohort fields (z-score, formula, lookup, etc.).

The recipe is the aggregator recipe with three swaps: a different type constant, a different registry, and a different skill file. The shape is otherwise identical.

1. Declare the type constant

Add the new constant to types/types.go and the slice returned by types.AllAttributeTypes():

const (
    // ... existing constants ...
    ATTR_GINI_BUCKET AttributeType = "ATTR_GINI_BUCKET"
)

func AllAttributeTypes() []AttributeType {
    return []AttributeType{
        // ... existing entries, alphabetised ...
        ATTR_GINI_BUCKET,
    }
}

Implement the attribute in processing/. Each attribute is a factory function registered in attributeRegistry (processing/registry.go). Attribute factories return a closure with the signature func(record encoding.RecordView) (any, error).

If the attribute can be evaluated row-at-a-time (the common case), that is all the implementation needs; the streaming Process path invokes the closure on every record.

3. Tests

Write tests first in processing/attribute_test.go. Run the suite, confirm informative failure, port the implementation until green.

4. Declare the capability metadata

Add a row to descriptor/capabilities_attributes.go with the attribute’s params, the field types it accepts as input, the type it emits, and any documentation strings. TestManifestOperatorsComplete enforces a capability row per registered attribute.

5. Update the attribute-composition skill

Add a section in skills/attribute-composition.md covering the new attribute’s params, output column naming convention, and any caveats (NaN propagation, integer underflow, expr-runtime cost). The TestSkillsCoverAllComponents gate parses the skill body for the operator name.

6. Update CLAUDE.md

Bump the count in CLAUDE.md’s “Skill Pack” section (the current registered counts line) so the registered-attribute total reflects the new operator.

7. Run the gates

go test ./skills/ -run TestSkillsCoverAllComponents
go test ./descriptor/ -run TestManifestOperatorsComplete
go test ./processing/ -run TestAttribute

The Update Demand row for attributes covers all of these in one PR; see The Update Demand.

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