---
name: yogsoth-ai/necessity-evaluation
source: https://app.decimal.ai/s/yogsoth-ai-necessity-evaluation@1/SKILL.md
source_sha256: f5f1cd7d5183
---

# Necessity Evaluation

Scores probability of necessity: P(Y would not hold | X absent).

## Execution

Subagent — spawned via subagent-spawning/spawn-agent.

## Why Subagent

Necessity evaluation requires careful counterfactual reasoning about absence, isolated from sufficiency judgments.

## Input

- **artifact**: The original artifact
- **factor**: The factor to evaluate for necessity
- **conclusion**: The conclusion that may depend on this factor

## Output

- **pn_score**: Probability of necessity (0.0–1.0)
- **reasoning**: Why this factor is/isn't necessary
- **alternative_paths**: Other ways the conclusion could hold without this factor
- **confidence**: Confidence in the PN estimate

## Budget

One unit = one necessity evaluation per factor.

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## Available SOPs

Optional, no fixed order; the final leaf is always a sop.

| SOP | When to use |
| --- | --- |
| spawn-agent | Spawn a customized CC subagent with full MCP tool access. Used by SOPs that declare execution: subagent. |

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