InvariantEval agent skill

InvariantEval enforces the invariants you declare. It does not make an agent "correct" and it does not rewrite output for you. The only honest claim: your agent runs your declared safety rules on every output and refuses to finalize when a locked field was auto-filled without human confirmation.

When to use this skill

Use before finalizing any structured JSON (or similar) output when:

• The domain has declared locked fields (pass/fail, compliance status, etc.)
• You have (or need) a suite.yaml with field_policies and invariant assertions
• A human is supposed to own certain fields and the model must not volunteer them

Do not use this skill to guess invariants. Your job is to make declaring them frictionless, not to infer them.

Workflow

1. Locate or create a declared suite

• Find an existing suite.yaml in the project, or
• Copy suite.template.yaml to the project and have the

user fill in field_policies, equivalence_classes, and assertions.

Never invent locked fields without user declaration in the suite.

2. Run the invariant check before finalize

You have the model's raw parsed output and the intended final output. Run:

python agent-skill/invarianteval/check.py \
  --suite path/to/suite.yaml \
  --case-id agent-check \
  --model-parsed /tmp/model_parsed.json \
  --final-output /tmp/final_output.json \
  --human-confirmed /tmp/human_confirmed.json

Write the JSON files from the current turn. --human-confirmed is optional (use {} when nothing was explicitly confirmed).

The suite must contain a case with the given --case-id (default: agent-check) and the assertions you want enforced.

3. If the check fails: STOP

• Do not finalize, commit, or present the output as complete.
• Surface the exact invariant failure from CLI output (e.g.

never_auto_filled[pass_fail_result]).

• Require one of:
• User edits the final output to remove or correct the violation, or
• User explicitly confirms the field (human_confirmed in the fixture), or
• User updates the declared suite if the rule was wrong (rare).

4. If the check passes: proceed

Finalize only after exit code 0.

MCP alternative

If the environment has the [mcp] extra installed, prefer the check_invariants MCP tool for the same inputs. See docs/mcp.md.

Honest framing (required)

• Say: "declared invariants", "refuses to finalize", "locked field auto-filled"
• Never say: "self-correct", "makes the agent correct", "auto-infer invariants"