Thin MCP server for GrowthBook — skill loader + authenticated API passthrough
Nothing to run from here
A/B Test Sample Size Calculator is installed from its publisher's own source and answers where it runs, so this marketplace is not in the path of a single call. There is no address here to send one to, and a panel that pretended otherwise would be showing you an answer we made up. Install it and call it from your own client — the Installation tab has the entry for each one.
96/100
tool-list score
5
tools declared
remote
at its publisher
—
calls last 7d
What it does
Exact A/B test sample size, duration, z-test, chi-square, Fisher-Freeman-Halton and peeking risk.
Quickstart
# 1 — add it to Claude Code
claude mcp add --scope user --transport http a-b-test-sample-size-calculator-mcp https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcp
# 2 — ask your agent for something these tools do
# calculate_sample_size, estimate_test_duration, test_ab_significance and 2 more
A/B Test Sample Size Calculator costs nothing on mcprush: there is no plan to choose here, no cap to set and nothing mcprush can bill you for.
Publishernot claimed
THAll 80 servers
theluckystrike80 servers
14 categories
Collected from a public index. Nobody has claimed this account, so nothing here was written by its author — claim it if it is yours.
Installation
Where are you running it?
Every route below installs the same thing and ends at the same approval screen. Nothing here runs on your machine and nothing runs on ours: this server answers at its publisher’s own address, and what you install is the connection straight to it.
Claude Codedeclared by this listing
This is a public server: it answers at its publisher’s own address and this marketplace is not in the path. Claude Code registers it in one command; --scope user makes it available in every project. The transport below is http, as the publisher's own manifest declares it.
claude mcp add --scope user --transport http a-b-test-sample-size-calculator-mcp https://ab-test-sample-size-calculator-mcp.lipmichal.workers.dev/mcpReconnect, or start a new session, and the tools appear in the model’s tool list.
Free on mcprush, and it answers at its publisher’s own address: this marketplace is not in the path, so there is no key of ours to hold and no card to add.
What it writes
One config entry pointing straight at the publisher’s own address — this marketplace is not in the path, and nothing from this listing executes on your machine.
What you approve
5 tools, with what each one reads, writes and reaches shown before you agree — the same list on every route above. Read the tool surface.
Tool surface
What the model actually sees. Descriptions are diffed on every release — see version history.
Exact sample size per variant for an A/B test on a conversion rate (two independent proportions): baseline rate, minimum detectable effect (relative or absolute), alpha, power, one or two-sided, several variants with optional Bonferroni, and unequal allocation. Uses the pooled/unpooled normal formula (same as R power.prop.test) and also reports the figure Evan Miller's calculator gives, so the two
| Parameter | Type | Required | Notes |
|---|---|---|---|
| baseline_rate | number | yes | Control conversion rate as a proportion, for example 0.042 for 4.2%. |
| mde | number | yes | Minimum detectable effect. Relative by default (0.10 = a 10% lift); set mde_type "absolute" for percentage points as a proportion (0.01 = 1 point). |
| mde_type | string | no | relative (default) or absolute. |
| alpha | number | no | Significance level, default 0.05. |
| power | number | no | Statistical power, default 0.80. |
| sided | string | no | two-sided (default) or one-sided test. |
| variants | integer | no | Number of arms including control. 2 = A/B, 3 = A/B/C. |
| bonferroni | boolean | no | Split alpha across the variant-vs-control comparisons (Bonferroni). |
| allocation_ratio | number | no | Users in each variant per user in control. 1 = even split. |
How many days an A/B test must run: from a known sample size per variant, or from baseline rate and MDE (computed as in calculate_sample_size), plus daily visitors and the share of traffic in the test. Returns exact days and the recommended whole weeks (to cover weekday effects).
| Parameter | Type | Required | Notes |
|---|---|---|---|
| daily_visitors | number | yes | Eligible visitors per day across the whole site or page. |
| traffic_share | number | no | Fraction of those visitors entered into the test, default 1. |
| sample_size_per_variant | integer | no | Known users per arm. If omitted, give baseline_rate and mde. |
| baseline_rate | number | no | Control conversion rate, for computing the sample size. |
| mde | number | no | Minimum detectable effect (relative by default). |
| mde_type | string | no | — |
| alpha | number | no | Significance level, default 0.05. |
| power | number | no | — |
| variants | integer | no | Number of arms including control. |
Is an A/B test result statistically significant? From visitors and conversions per group: two-proportion z-test (pooled), one or two-sided p-value, Wald confidence interval for the difference, relative lift, Pearson chi-square with and without Yates correction (R prop.test), Fisher exact p for the same 2x2 table, and a sample ratio mismatch (SRM) check against the planned split.
| Parameter | Type | Required | Notes |
|---|---|---|---|
| control_visitors | integer | yes | — |
| control_conversions | integer | yes | — |
| variant_visitors | integer | yes | — |
| variant_conversions | integer | yes | — |
| alpha | number | no | Significance level, default 0.05. |
| alternative | string | no | greater = variant converts better than control. |
| expected_split | number | no | Planned share of traffic in control, for the SRM check. Default 0.5. |
Exact p-value for a contingency table of counts. 2x2: Fisher exact test (two-sided, greater or less, as R fisher.test). Larger r x c tables (for example 3 variants x converted/not, or 4 x 4 survey tables): Fisher-Freeman-Halton exact test by a network algorithm. Also returns Pearson chi-square and how many cells have expected counts below 5, so you can see when the chi-square approximation is unsa
| Parameter | Type | Required | Notes |
|---|---|---|---|
| table | array | yes | Rows of counts, for example [[12, 488], [25, 475]] (rows = groups, columns = outcomes). |
| alternative | string | no | One-sided options apply to 2x2 only; greater = odds ratio above 1. |
What peeking does to an A/B test: the real false positive rate if you check a fixed-horizon test K times and stop at the first p < alpha (for example about 14% at 5 looks with alpha 0.05), and the Pocock and O'Brien-Fleming group sequential boundaries (z and nominal p per look) that keep the overall rate at alpha, for up to 10 equally spaced looks.
| Parameter | Type | Required | Notes |
|---|---|---|---|
| looks | integer | yes | How many times the result is checked, including the final look. Equally spaced. |
| alpha | number | no | Significance level, default 0.05. |
Free
$0 forever
- Every tool — any call limit is its publisher’s, not ours
- No card, and mcprush charges nothing for it
- Runs at its publisher’s own address — this marketplace is not in the path
- Nothing to cap, because mcprush bills nothing
What counts against your monthly calls
| Tool | Unit | Calls used | Out of the allowance |
|---|
Nothing here is billable: mcprush charges nothing to install A/B Test Sample Size Calculator or to call it, at any volume.
Call allowance · this installenforced at the gateway
Monthly allowance, in calls
—
—
Alert at 80% · then the tool returns a normal MCP error
Used this month: —
ATool-list grade · score 96 / 100
Release 1.0.0 · scanned 2 Nov 2026
Graded from the tools this server lists, not from its source code.
Two independent axes, because powerful and malicious are different questions. The grade is threat only. The capability level is blast radius, and it is never a penalty on the grade — it is priced as one subtract-only term in the score, where you can see it.
Threat score100
Client score96
Findings0 threat · 0 capability
Capabilityminimal
Coveragemanifest
Verificationnot in this report
Surface digestce739ea709720ee461cb9c6681145ccc042e5510d5647ac5a17700271a024f77
Score vectorthreat 100 → client 96
| Term | Level | What it prices | Points |
|---|---|---|---|
| capability-exposure | minimal | capability blast radius (minimal) — client exposure if the model is manipulated | −0 |
| coverage-honesty | manifest | inspection depth (manifest) — how much of the target the scan could see | −4 |
score = clamp(round(threatScore − E_cap − E_ver − E_cov), 0, 100). No model, no opinion, no network call at scoring time: the same methodology version against the same bytes always produces this number, and every line above is a field of the report rather than a summary of it.
What the scan could actually read
A grade is only as meaningful as its coverage, so the scanner publishes its own depth before it publishes its result.
The scan read each tool’s name, description, input schema and annotations exactly as the server listed them the last time it answered us; no code was reviewed. We ask the server again about once a month, and a list that changed is graded again.
Tool surfaceread
Implementation sourcenot available
Package metadatanot available
Live transportnot available
The implementation source was not read — this reflects the declared tool metadata only.
Capability — what it could do if the model were manipulated
Tags derived from each tool’s schema and the implementation, not from what the tool calls itself. minimal is the level these add up to.
| Tool | Capability tags | Why the tag was assigned |
|---|---|---|
| calculate_sample_size | no tags | |
| estimate_test_duration | no tags | |
| test_ab_significance | no tags | |
| fisher_exact_test | no tags | |
| check_peeking_risk | no tags |
Toxic-flow graph
The lethal trifecta, checked as a graph rather than as a checklist: untrusted input, a sensitive source and an external sink have to meet before there is a path worth worrying about.
The public result for this release does not print the flow graph, so there is nothing to show here. That is not the same as "no paths were found": what the scan did read is above, under coverage.
Supply chain and provenance
Integrityfirst-seen
Surface digestce739ea709720ee4
Scanned2026-11-02
This is the first scan of this surface here, so there is nothing yet to compare it against.
Every result on this tab comes from one deterministic pass over the published package — offline, rule by rule, and auditable line by line above. Same methodology version, same bytes, same score.
Release history
This is an address its publisher runs: which release it serves is theirs to choose, so there is nothing here to pin. The history below is for reading; the current release on file is 1.0.0.
1.0.0
undated
latestNo release note was published with this version.
—
no reviews yet
Who can review
One review per account, from a signed-in account that does not publish this listing. Nothing else is asked — you can say what you think before you install it. Publishers can reply once per review, and a review can be edited or deleted by whoever wrote it.
Sign in to write one
Any signed-in account that does not publish A/B Test Sample Size Calculator can review it, once — before installing it or after. A review from an account that has installed it is marked as one.
No reviews yet
Nobody has reviewed this listing. The rating on the card is the mean of the reviews written here and nothing else, so there is no rating until somebody writes the first — which takes a signed-in account that does not publish it, and nothing else.