gs-design-specialist

gs-design-specialist is an agent for Claude Code from choxos/BiostatAgent. It costs 28 tokens per session (2,131 once invoked), scanned A, original, MIT.

An agent that helps design and simulate group sequential clinical trials. These trials include planned interim analyses so a study may stop early for success or futility.

In plain words
What is it for?
Use it for alpha-spending functions, futility boundaries, information fractions, and simulations with simtrial's sim_gs_n(), including designs derived with gsDesign2.
Why use it?
It helps choose interim-analysis timings, control the overall false-positive rate, and set rules for stopping a trial early. It also helps assess how design choices affect stopping probabilities and expected sample size.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the clinical-trial-simulation plugin — 7 skills, 5 commands, 7 agents shipped together

Good fit Use it for alpha-spending functions, futility boundaries, information fractions, and simulations with simtrial's sim_gs_n(), including designs derived with gsDesign2.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/choxos/biostatagent/gs-design-specialist
Install

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.

Clone the repo
git clone --depth 1 https://github.com/choxos/BiostatAgent

Made for: Claude Code.

Or install clinical-trial-simulation, the plugin that ships this one along with the rest of its 7 skills, 5 commands, 7 agents.

Wrote 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.

agentmods badge for gs-design-specialist

README.md
[![agentmods](https://agentmods.dev/badge/agents/choxos/biostatagent/gs-design-specialist/github.svg)](https://agentmods.dev/agents/choxos/biostatagent/gs-design-specialist)
Your own site
<a href="https://agentmods.dev/agents/choxos/biostatagent/gs-design-specialist"><img src="https://agentmods.dev/badge/agents/choxos/biostatagent/gs-design-specialist/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.

agentmods 80×15 button for gs-design-specialist

Your own site · 80×15
<a href="https://agentmods.dev/agents/choxos/biostatagent/gs-design-specialist"><img src="https://agentmods.dev/badge/agents/choxos/biostatagent/gs-design-specialist.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 28 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,131 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00028 $0.02131
Opus 5 $0.00014 $0.01066
Sonnet 5 $0.00006 $0.00426
Haiku 4.5 $0.00003 $0.00213

Measured 9d ago against content hash d8a480f2fcf5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

gs-design-specialist 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.

plugins/clinical-trial-simulation/agents/gs-design-specialist.md · 271 lines

How it starts

The opening of the file, as written. The whole thing — 271 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Group Sequential Design Specialist

Purpose

You are a specialist in group sequential trial designs with interim analyses. You help users design trials with early stopping opportunities, configure alpha spending functions, implement futility rules, and run simulations using simtrial's sim_gs_n().

Core Capabilities

Design Configuration

  • Select appropriate number and timing of interim analyses
  • Configure alpha spending functions (OBF, Pocock, HSD)
  • Set up futility boundaries (binding vs non-binding)
  • Calculate information fractions

Simulation

  • Use sim_gs_n() for GS simulations
  • Create cutting functions with create_cut()
  • Integrate with gsDesign2 for design derivation
  • Compute updated bounds based on actual information

Analysis

  • Evaluate operating characteristics
  • Calculate stopping probabilities
  • Assess expected sample size savings
  • Compare spending function choices

Knowledge Base

Spending Function Selection

Scenario Recommended Rationale
Standard regulatory OBF Conservative, preserves final power
Large expected effect Pocock Easier early stopping
Uncertain effect size HSD(γ=-2) Moderate compromise
Survival with delay OBF with weighted LR Maintains power for late effects

Information Timing Guidelines

# Analyses Typical Information Fractions
2 50%, 100%
3 33%, 67%, 100%
4 25%, 50%, 75%, 100%

Futility Decision Framework

Conditional Power Recommendation
< 10% Strong case for futility
10-20% Consider futility
20-50% Continue with caution
> 50% Continue

Behavioral Traits

  1. Regulatory-Aligned: Follow ICH E9 and agency guidance
  2. Conservative-Default: Recommend OBF unless justified otherwise
  3. Simulation-Validated: Always validate designs with simulation
  4. DSMB-Aware: Consider unblinded review processes
  5. Documentation-Focused: Emphasize pre-specification

Read the full file on GitHub · 271 lines

Changes

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.

  1. 9d ago First seen · 271 lines · 28 tokens per session scan A d8a480f2fcf5

Subscribe to this mod's changes

gs-design-specialist is an agent published in the GitHub repository choxos/BiostatAgent (11 stars, last pushed 3mo ago), licensed MIT. It adds 28 tokens to every session and 2,131 once invoked, about $0.0001 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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