Assumption check Agent Skill

Audit something Claude built for the unstated assumptions baked into it — the silent interpretive leaps, not the caveats already written…

Context cost
4.5k tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 18.1 kBtext throughout, nothing executable
Licence
not declarednone named by its author
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Audit something Claude built for the unstated assumptions baked into it — the silent interpretive leaps, not the caveats already written down. Reports each one with what would change if it is wrong and the one question that settles it. Use ONLY when the user explicitly invokes it. Do NOT auto-trigger on finishing a piece of work, do NOT run it on work still in progress, and do NOT use it as a general critique or code-review tool.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

productivity

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md18.1 kB · preview
--- name: assumption-check ---
6# Assumption check
7
8**When this is invoked, run the audit. Don't explain the skill back to the user; running it is the job.**
9
10## What a good result looks like
11
12**Returning nothing is a completed job, not a failed one.** On a well-made artifact the expected answer is that there is nothing to report. A run that surfaces one marginal finding on a clean document has done **worse** than one that surfaces none — it spends the reader's attention and teaches them your findings aren't worth checking.
13
14The pull toward reporting *something* is the largest source of error here, and it has beaten every rule written to contain it. Measured on two clean controls, it was the sole cause of every false positive. **Zero is valid, expected, and frequently correct.**
15
16## What you are looking for
17
18Not stated caveats. *"Assumption: Q3 figures are final"* already announced itself — it is not a finding.
19
20You want the leaps that were made **silently**. The canonical case: a column named rev_net was read as net of refunds, when it was net of tax. Nobody wrote it down. The report was built on it.
21
22## What you cannot know, and must say so
23
24You cannot know how *likely* an assumption is to be wrong. That is a fact about the client's schema, their conventions, their world — and the artifact is, by construction, the thing that does not contain it. If it did, there would be no assumption.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md3,102 words
Files1
Licencenot declared
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈120
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
4,405
on trigger
The instruction body, read only when the skill fires.
2.3%
of a 200k window
Ten skills this size would take about 23% of the window before you open a file.
050k100k150k200k context window

4.5k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

1 file, 18.1 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md18.1 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Assumption check · 4.5k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/assumption-check/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/assumption-check" ] && { [ ! -e .claude/skills/assumption-check ] || { mv .claude/skills/assumption-check "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/assumption-check" .claude/skills/ && echo "Installed .claude/skills/assumption-check"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add epam-adrian/assumption-check

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/assumption-check/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/assumption-check/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/assumption-check" ] && { [ ! -e ~/.claude/skills/assumption-check ] || { mv ~/.claude/skills/assumption-check "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/assumption-check" ~/.claude/skills/ && echo "Installed ~/.claude/skills/assumption-check" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/assumption-check/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referenceepam-adrian/assumption-check

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

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