| name | txscript-reference |
| description | Rossum field-expression reference for TxScript serverless hooks, native Rossum Rule trigger_condition expressions, and schema-field formulas. Covers (a) TxScript Python 3.12 API, (b) the native Rule trigger_condition expression language and the defensive is_empty guard convention (the Rule entity, actions[], and FIRE-vs-PASS polarity live in business-rules-reference), and (c) schema-field formula expressions (default_to, is_set, is_empty, line-item .all_values, helpers, multi-line formulas, the "absorb" refactoring pattern, and when formulas do and do not recompute — a queue move carries values across without re-evaluating them). Use when writing or debugging any Rossum field-expression code — a hook .py file, a Rule trigger_condition, or a schema formula. |
| user-invocable | false |
Rossum Field-Expression Reference: TxScript, Rules, Formulas
This skill is the practical reference for every Rossum surface that runs a Python-flavored expression on annotation data:
- TxScript serverless hooks (
.py files invoked by webhook events) — full Python 3.12, with the TxScript helper class.
- Native Rule
trigger_condition expressions (POST /v1/rules) — the boolean condition language. The Rule entity, actions[], and FIRE-vs-PASS polarity are documented in the business-rules-reference skill.
- Schema-field formulas (
formulas/<field_id>.py next to schema.json) — multi-line Python expressions where the last expression is the field's value.
All three share the same Python expression sublanguage (operators, comparisons, helpers like default_to / is_empty) but the evaluation context differs (event-driven hook vs. validation-time rule vs. derived-field formula). See reference.md for the full reference; the rest of this SKILL.md indexes when to consult what.
IMPORTANT — editing rule:
- For hook code: always edit the
.py file next to the hook JSON. Never edit the code field inside the hook's .json. prd2 extracts hook code into .py files on pull and merges it back on push.
- For formulas: always edit
formulas/<field_id>.py next to schema.json. Never edit the formula property inside schema.json directly. prd2 handles the round-trip.
- For Rules: edit the rule JSON directly (
trigger_condition is a string field, not extracted into a .py).
Use this knowledge when:
- Writing or debugging a TxScript serverless hook (the original audience)
- Writing a native Rule
trigger_condition expression (the Rule entity and actions[] live in business-rules-reference)
- Authoring a schema-field formula (single-expression or multi-line)
- Working out when a formula (re)evaluates — in particular that a plain queue move carries values across without recomputing them
- Looking up common schema field IDs and their conventions
Cross-references:
business-rules-reference covers the rule/validation feature: the native Rule entity, actions[], and FIRE-vs-PASS polarity, plus the legacy Business Rules Validation extension and its own {field}-brace expression engine.rossum-reference covers the platform overall.prd-reference covers the local file layout and prd2 push/pull workflow.
