What is evo-stl-mass?

A tool for reading binary STL files, which store the triangle shape of a 3D object, and calculating the mass of the main part from its material and volume.

Use it to estimate the mass of a 3D-printed part from STL scan data, including separating the largest connected piece and identifying its material.

It removes the need to manually discard loose scan debris, measure the enclosed shape, and look up material density. It also produces a report that can be checked for validity.

evo-stl-mass — Skill for Claude Code and Codex by Zhang-Henry

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.

Any agent

npx skills add Zhang-Henry/CoEvoSkills --skill evo-stl-mass

Clone the repo

git clone --depth 1 https://github.com/Zhang-Henry/CoEvoSkills

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/zhang-henry/coevoskills/evo-stl-mass/github.svg)](https://agentmods.dev/skills/zhang-henry/coevoskills/evo-stl-mass)

Your own site

<a href="https://agentmods.dev/skills/zhang-henry/coevoskills/evo-stl-mass"><img src="https://agentmods.dev/badge/skills/zhang-henry/coevoskills/evo-stl-mass/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/zhang-henry/coevoskills/evo-stl-mass"><img src="https://agentmods.dev/badge/skills/zhang-henry/coevoskills/evo-stl-mass.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 436 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. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00043	$0.00436
Opus 5	$0.00022	$0.00218
Sonnet 5	$0.00009	$0.00087
Haiku 4.5	$0.00004	$0.00044

Measured 12d ago against content hash 316f3f5185c4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

evo-stl-mass 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 12d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/utils.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

artifacts/skills/3d-scan-calc/evo-stl-mass/SKILL.md · 49 lines

What it actually says

STL Mass Calculation Skill

This skill parses binary STL files where the 2-byte attribute field stores a Material ID, finds the largest connected component (filtering out debris), computes the enclosed volume using signed tetrahedra, and calculates mass using a material density lookup table.

Quick Start

import sys
sys.path.insert(0, '/app/environment/skills/evo-stl-mass/scripts')
from utils import compute_mass, validate_report

result = compute_mass(
    stl_path='/root/scan_data.stl',
    density_table_path='/root/material_density_table.md',
    output_path='/root/mass_report.json'
)
print(result)

validate_report('/root/mass_report.json')

Key Functions

parse_binary_stl(filepath) - Parse binary STL, extract triangles with material IDs
find_connected_components(triangles, tolerance) - Union-Find based component detection
compute_mesh_volume(triangles, indices) - Signed tetrahedra volume calculation
get_component_material_id(triangles, indices) - Majority vote material ID
parse_density_table(filepath) - Parse markdown density table
compute_mass(stl_path, density_table_path, output_path) - End-to-end entry point
validate_report(output_path) - Validate output JSON

Algorithm

Parse binary STL: 80-byte header + 4-byte count + N*50-byte records
Each record: 12 floats (normal + 3 vertices) + 2-byte attribute (Material ID)
Build vertex adjacency with tolerance-based matching
Union-Find to group connected triangles
Select largest component by triangle count
Compute volume via signed tetrahedra sum
Convert units (mm^3 to cm^3 if needed)
Look up density and compute mass

Files

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.

scripts/utils.py 9.2 KB runs code

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.

12d ago First seen · 49 lines · 43 tokens per session scan A 316f3f5185c4

Subscribe to this mod's changes

evo-stl-mass is a skill published in the GitHub repository Zhang-Henry/CoEvoSkills (66 stars, last pushed 22d ago), licensed Apache-2.0. It adds 43 tokens to every session and 436 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 2026-08-30.

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