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 CassioRoos/godfly-skills --skill assumptions-checkgit clone --depth 1 https://github.com/CassioRoos/godfly-skillsWrote 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/cassioroos/godfly-skills/assumptions-check)<a href="https://agentmods.dev/skills/cassioroos/godfly-skills/assumptions-check"><img src="https://agentmods.dev/badge/skills/cassioroos/godfly-skills/assumptions-check/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/cassioroos/godfly-skills/assumptions-check"><img src="https://agentmods.dev/badge/skills/cassioroos/godfly-skills/assumptions-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00048 | $0.00941 |
| Opus 5 | $0.00024 | $0.00470 |
| Sonnet 5 | $0.00010 | $0.00188 |
| Haiku 4.5 | $0.00005 | $0.00094 |
Grade A, and why
assumptions-check 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 3d 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 — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Key Assumptions Check
Surface what's being taken for granted. Test it. Break what's fragile before it breaks you.
Core Principle
Every plan, design, and decision rests on assumptions -- most of them invisible. This skill makes them visible, rates their strength, and identifies which ones need evidence or testing before you proceed.
When to Use
Use when an assumptions inventory is the requested deliverable, or a specific unverified assumption warrants this technique. Do not run a separate inventory for every non-trivial decision. Examples within that scope:
- Before committing to an architecture or technology bet
- When a plan feels "obviously right" (that's when assumptions hide best)
- When reviewing code that makes implicit guarantees
- When someone says "that won't be a problem" without evidence
- When inherited designs carry forward without re-examination
The Process
Step 1: Extract Assumptions
Read the plan/code/design and list every assumption -- stated or implied.
Look for assumptions in these categories:
| Category | What to look for |
|---|---|
| Technical | "This library handles X", "The database can handle Y load", "This API is reliable" |
| User | "Users will do X", "Users understand Y", "Users won't do Z" |
| Business | "We have time for X", "The market wants Y", "Competitors won't Z" |
| Team | "We have expertise in X", "We can hire for Y", "This won't need maintenance" |
| Environment | "Infrastructure supports X", "Latency will be under Y", "Data volume won't exceed Z" |
Step 2: Rate Each Assumption
| Rating | Meaning | Action |
|---|---|---|
| Verified | Tested, measured, or proven with data | Document the evidence |
| Confident | Strong reasons to believe, but not tested | Note the reasoning |
| Uncertain | Could go either way, no strong evidence | Needs investigation |
| Untested | Never examined, just accepted | Needs immediate testing |
| Fragile | Evidence suggests it might be wrong | Challenge now |
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.
- 3d ago Changed · -3 lines · -39 tokens per session 7d021c69b5cc
- 12d ago First seen · 108 lines · 87 tokens per session scan A 286a755b98b4
assumptions-check is a skill published in the GitHub repository CassioRoos/godfly-skills (1 stars, last pushed 2d ago), licensed MIT. It adds 48 tokens to every session and 941 once invoked, about $0.0002 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 2026-08-31.
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