Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add jabrena/plinth --skill 023-assumption-analysisgit clone --depth 1 https://github.com/jabrena/plinthWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jabrena/plinth/023-assumption-analysis)<a href="https://agentmods.dev/skills/jabrena/plinth/023-assumption-analysis"><img src="https://agentmods.dev/badge/skills/jabrena/plinth/023-assumption-analysis/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jabrena/plinth/023-assumption-analysis"><img src="https://agentmods.dev/badge/skills/jabrena/plinth/023-assumption-analysis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00079 | $0.00691 |
| Opus 5 | $0.00039 | $0.00345 |
| Sonnet 5 | $0.00016 | $0.00138 |
| Haiku 4.5 | $0.00008 | $0.00069 |
Grade A, and why
023-assumption-analysis scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Assumption Analysis
Guide production of explicit Assumptions, a list of Unknowns, and a Validation plan for a problem under exploration. This is an interactive SKILL.
What is covered in this Skill?
- Surfacing assumptions implicit in the problem frame and root-cause findings
- Distinguishing an assumption (believed true, not yet verified) from an unknown (not yet known either way)
- Ranking assumptions and unknowns by impact and confidence
- Defining a validation plan that names how and when each risky assumption or unknown will be checked
- Feeding assumption and unknown findings into
024-context-mappingand the remaining Functional Specification lenses
Constraints
Make assumptions and unknowns explicit before they become undiscussed risk. When this technique is orchestrated by another workflow, the orchestrator owns clarifying-question sequencing; when applied standalone, ask directly.
- MUST read
references/023-assumption-analysis.mdbefore applying Assumption Analysis guidance - MUST state each assumption as a falsifiable claim believed true but not yet verified
- MUST distinguish assumptions (believed true) from unknowns (not yet known either way)
- MUST rank assumptions and unknowns by impact if wrong and by current confidence
- MUST define a validation plan naming how and when each high-impact, low-confidence assumption or unknown will be checked
- MUST NOT invent an assumption, unknown, or validation step when the available content is vague or ambiguous; flag the gap for a clarifying question instead
When to use this skill
- Surface the assumptions behind this problem
- List the unknowns for this issue
- Build a validation plan for these assumptions
- Apply assumption analysis before design begins
- Draft the Assumption Analysis section of a Functional Specification
Workflow
- Read the Reference
Read references/023-assumption-analysis.md, then review the problem frame and root-cause findings for implicit beliefs.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 69 lines · 79 tokens per session scan A aa59509c2610
023-assumption-analysis is a skill published in the GitHub repository jabrena/plinth (437 stars, last pushed yesterday), licensed Apache-2.0. It adds 79 tokens to every session and 691 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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