Secure Software Engineering Agent Skill

Use when designing or implementing software securely: define security requirements, threat-model a feature, choose secure defaults, design…

Context cost
12.3k tokensestimated from the bundle, loaded when it triggers
Bundle
17 files · 49.0 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Use when designing or implementing software securely: define security requirements, threat-model a feature, choose secure defaults, design authentication and authorization, handle untrusted data and secrets, evaluate dependencies, design multi-tenant trust boundaries, or review security-sensitive changes. Use for prevention during requirements, design, implementation, and review; not for post-build security assessments or scanning an existing codebase.

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.

securitytesting

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.md6.3 kB · preview
--- name: secure-software-engineering license: MIT ---
13# Secure Software Engineering
14
15Build security into decisions before defects reach production. This is a prevention-oriented workflow, not a claim that a design or release is secure. Record assumptions, the evidence collected, residual risks, and the owner of any accepted exception.
16
17## When To Use
18
19Use this skill to answer "How do we build this securely?" for a new feature, integration, service, API, tenant boundary, AI capability, or release. Start early and revisit affected decisions when architecture, data flows, dependencies, or threats change.
20
21Do not use it for an authorized post-build assessment or as a vulnerability scanner for an existing codebase; use an authorized scanning tool or specialist security assessment. When formalizing the resulting requirements, use the repository's normal specification workflow and make completion claims only from direct verification evidence.
22
23## When not to use
24
25End-to-end tenant models, control/application-plane placement, commercial lifecycle, capacity planning, and SaaS operating architecture are outside this skill; it owns the threat model and enforceable isolation controls. Route privacy lifecycle and deletion-verification artifacts to the project's privacy owner.
26
27## Workflow
28
291. **Requirements**: identify assets, actors, harm, data classifications, regulatory or contractual constraints, and security outcomes. Write testable acceptance criteria before selecting controls.
302. **Threat model**: map data flows and trust boundaries; state assumptions, abuse cases, mitigations, and residual risk. STRIDE is optional vocabulary, not an exhaustive method.
313. **Design**: choose controls that fit the trust model, including server-side authorization, data isolation, safe failure behavior, and AI capability boundaries. Explain rejected alternatives.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md745 words
Files17
LicenceMIT
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.

≈130
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
12,120
on trigger
The instruction body and 16 supporting files, read only when the skill fires.
6.1%
of a 200k window
Ten skills this size would take about 61% of the window before you open a file.
050k100k150k200k context window

12.3k 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

17 files, 49.0 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md6.3 kB
  • LICENSE.txt1.1 kB
  • references/ai-llm-security.md2.6 kB
  • references/authentication-authorization.md2.1 kB
  • references/dependency-supply-chain.md2.0 kB
  • references/incident-learning.md1.7 kB
  • references/input-validation-data-handling.md2.0 kB
  • references/multi-tenant-isolation.md9.2 kB
  • references/release-evidence.md1.9 kB
  • references/secrets-lifecycle.md1.8 kB
  • references/secure-code-review.md1.9 kB
  • references/secure-logging-audit.md1.9 kB
  • references/security-requirements-threat-modeling.md3.6 kB
  • references/source-index.md4.1 kB
  • templates/lightweight-threat-model.md2.4 kB
  • templates/secure-code-review-checklist.md2.1 kB
  • templates/security-acceptance-criteria.md2.3 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 17 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

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

# Secure Software Engineering · 12.3k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/secure-software-engineering/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/secure-software-engineering" ] && { [ ! -e .claude/skills/secure-software-engineering ] || { mv .claude/skills/secure-software-engineering "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/secure-software-engineering" .claude/skills/ && echo "Installed .claude/skills/secure-software-engineering"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add zolkyed/secure-software-engineering

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/secure-software-engineering/ 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/secure-software-engineering/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/secure-software-engineering" ] && { [ ! -e ~/.claude/skills/secure-software-engineering ] || { mv ~/.claude/skills/secure-software-engineering "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/secure-software-engineering" ~/.claude/skills/ && echo "Installed ~/.claude/skills/secure-software-engineering" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/secure-software-engineering/ 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
Referencezolkyed/secure-software-engineering

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.

Reviews

—no reviews yet

Nobody has reviewed this skill yet. The rating is the mean of the reviews written here, so there is none until somebody writes the first.

Sign in to review it

A review is tied to an account so it can be answered, edited and taken down by the person who wrote it.

Sign in
Who can post

Anybody with an account, one review each. It carries the version that was current when you wrote it, and the publisher may reply once.

Publisher
Servers0
Claim this skill