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 agentmods add skills/zebbern/claude-code-guide/project-sizing-guidenpx skills add zebbern/claude-code-guide --skill project-sizing-guidegit clone --depth 1 https://github.com/zebbern/claude-code-guideWhat 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 | $0.00086 | $0.03104 |
| Opus 5 | $0.00043 | $0.01552 |
| Sonnet 5 | $0.00017 | $0.00621 |
| Haiku 4.5 | $0.00009 | $0.00310 |
Grade A, and why
project-sizing-guide 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 2d 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 — 291 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Project Sizing Guide — Software Project Effort Estimation
Helps teams produce scientifically grounded effort estimates for software projects, based on three major methodologies: Three-Point Estimation (PERT), T-shirt Sizing, and Function Point Analysis (FPA). Outputs optimistic, most-likely, and pessimistic values along with risk intervals.
Quick Start
- User provides a requirements description → Agent identifies functional modules and breaks them into a Work Breakdown Structure (WBS)
- Select an estimation method → Choose the best-fit approach based on project stage and available information
- Estimate each item → Assign O/M/P (Optimistic / Most Likely / Pessimistic) values to every work package
- Aggregate and report → Generate an estimation report with risk analysis and confidence intervals
A calculation helper is available:
python3 scripts/estimate_calculator.py --method pert --tasks '[{"name":"User Login","O":2,"M":3,"P":8}]'
Method Selection Guide
| Scenario | Recommended Method | Rationale |
|---|---|---|
| Early feasibility study, rough budgeting | T-shirt Sizing | Little information available; quickly align on order of magnitude |
| Sprint planning, iteration estimation | Three-Point Estimation (PERT) | Good granularity with confidence intervals |
| Contract bidding, large-project RFPs | Function Point Analysis (FPA) | Most rigorous; industry-comparable |
| Team has historical data | PERT + historical calibration | Combines empirical correction with data |
Method 1: Three-Point Estimation (PERT)
Core Formulas
| Metric | Formula | Meaning |
|---|---|---|
| Expected Value E | (O + 4M + P) / 6 | Weighted average effort |
| Standard Deviation σ | (P − O) / 6 | Estimation uncertainty |
| Variance V | σ² | Used to aggregate across tasks |
| Project Total Expected | ΣE | Sum of individual expected values |
| Project Total Std Dev | √(ΣV) | Square root of summed variances |
What ships with it
2 files 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.
- 2d ago First seen · 291 lines · 86 tokens per session scan A 0ab796082c50
project-sizing-guide is a skill published in the GitHub repository zebbern/claude-code-guide (4,597 stars, last pushed yesterday), licensed MIT. It adds 86 tokens to every session and 3,104 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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