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Agent skill

System Design Interview Coaching

by HoangNguyen0403 in HoangNguyen0403/agent-skills-standard

Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion…

MITAuto-check passedEducation

Install System Design Interview Coaching

skills CLI
$ npx skills add HoangNguyen0403/agent-skills-standard --skill system-design-interview-coaching -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install HoangNguyen0403/agent-skills-standard system-design-interview-coaching --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/HoangNguyen0403/agent-skills-standard.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/system-design/system-design-interview-coaching .claude/skills/system-design-interview-coaching && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
system-design-interview-coaching
GitHub stars
572
Token cost
~1.3k tokens
SKILL.md length
639 words
Files
6 (incl. references)
Skills in repo
211
Repo updated
First seen
Licence
MIT

At a glance

Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion…

  • Works in 7 steps: Open with the problem, the length (45… → Run the seven phases in order per time… → When a phase overruns, interrupt with… → …
  • Interview practice
  • SKILL.md covers Priority: P1 (HIGH), Roles, Round Protocol and Rules, plus 5 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

System Design Interview Coaching is an agent skill from HoangNguyen0403/agent-skills-standard. Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion 0-3 rubric with quoted evidence. Use for interview practice, prep, or grading a practice design.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including reference files (for example `evals/evals.json`, `references/mistakes.md` and `references/rubric.md`).

It sits in Education, covering Software architecture, Quizzes and assessments and Diagrams. It works with Mermaid. The repository describes itself as: A collection of Agent Skills Standard and Best Practice for Programming Languages, Frameworks that help our AI Agent follow best practies on frameworks and programming laguages. The licence is MIT.

When your agent uses it

  • Interview practice
  • Grading a practice design

Example prompts

  • “/system-design-interview-coaching”

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

  1. Open with the problem, the length (45 minutes unless told otherwise), and "start by scoping it". Start the clock.
  2. Run the seven phases in order per time budget: requirements, estimation, high-level design, data model, API, deep dive, bottlenecks.
  3. When a phase overruns, interrupt with the remaining time and the next phase's question ("Two minutes left in estimation. What is the…
  4. Once, around the deep dive, change one requirement deliberately (read ratio, retention, consistency). Absorbing it is expected and scored.
  5. Push on the weakest area with one follow-up, not a list of gaps.
  6. Give the model answer only after the candidate commits to an approach, and only for the part they committed to.
  7. Stop at time. Debrief per rubric: six criteria scored 0-3, quoted evidence per score, two fixes first, next practice problem.

What it can do on your machine

Read from SKILL.md and the folder at commit b529c2d. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

System Design Interview Coaching loads about 1.3k tokens when it runs, and up to ~3.7k if it reads all its reference files. Until then it costs about 82 tokens; SKILL.md has 639 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~82
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~3.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from HoangNguyen0403/agent-skills-standard at commit b529c2d, republished under its MIT licence (© HoangNguyen0403). 639 words, ~1,266 tokens.

Download SKILL.mdSave it as .claude/skills/system-design-interview-coaching/SKILL.md (or your agent's skills folder). This skill also uses 5 other files; get the full folder from GitHub.
name
system-design-interview-coaching
description
Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion 0-3 rubric with quoted evidence. Use for interview practice, prep, or grading a practice design.

System Design Interview Coaching

Priority: P1 (HIGH)

Be the interviewer during the round and the coach after it. Never design for the candidate mid-round.

Roles

  • Interviewer during the round: states the problem and the clock, answers scoping questions tersely, changes a requirement on purpose once, tracks time.
  • Coach after it: scores with the rubric, quotes the candidate's own words as evidence, names the two fixes to work on first.
  • The candidate talks 80 % of the time; the interviewer 20 %. A monologue from the interviewer is a failed round.

Round Protocol

  1. Open with the problem, the length (45 minutes unless told otherwise), and "start by scoping it". Start the clock.
  2. Run the seven phases in order per time budget: requirements, estimation, high-level design, data model, API, deep dive, bottlenecks.
  3. When a phase overruns, interrupt with the remaining time and the next phase's question ("Two minutes left in estimation. What is the shaping quantity?").
  4. Once, around the deep dive, change one requirement deliberately (read ratio, retention, consistency). Absorbing it is expected and scored.
  5. Push on the weakest area with one follow-up, not a list of gaps.
  6. Give the model answer only after the candidate commits to an approach, and only for the part they committed to.
  7. Stop at time. Debrief per rubric: six criteria scored 0-3, quoted evidence per score, two fixes first, next practice problem.

Rules

  • Numbers before boxes: no component until the shaping quantity exists; a guessed number labelled ASSUMED is fine, a missing one is not.
  • No buzzword without a reason: "NoSQL", "Kafka", "sharding" earn a follow-up "why this, here" every time.
  • No component without a constraint: each box answers "what breaks without it".
  • A changed requirement is deliberate: expected, and scored under trade-offs.
  • Silence is not help: when the candidate stalls for a minute, ask one question that names the phase, never the answer.

Sketching

  • During the round: Mermaid inline in chat, at most one sketch per phase, per whiteboard rules. Same conventions as the house style: labelled arrows, dashed for async, one level per sketch, acronyms expanded, assumptions marked ASSUMED.
  • After the round: the model answer may be rendered through common-architecture-diagramming when a real system sits behind the practice; a classic catalog problem stays as Mermaid.
Show full SKILL.md (263 more words)Show less

Debrief

  • Score each of the six criteria 0-3 with one quoted line from the round as evidence; totals map to bands (strong hire, hire, borderline, no hire).
  • Name the two fixes to work on first, each tied to a row in mistakes.
  • Recommend the next practice problem from system-design-case-catalog that exercises the weakest criterion.

Anti-Patterns

  • No answer dump: the value is the questions asked; the model answer waits for a commitment.
  • No skipped estimation: "I know this one" still needs this problem's numbers.
  • No score without evidence: a number with no quote is an opinion, not feedback.
  • No hire inflation: the band follows the total; confidence is not a criterion.
  • No production plan: an interview answer omits migration, cost, compliance, and team constraints; say so once, do not grade on them.

Red Flags

ThoughtReality
"Just tell me the answer"The model answer comes after the candidate commits to an approach, and only for that part.
"I know this one, skip the numbers"Numbers before boxes. Estimation is the phase most rounds fail on.
"We're out of time, dump the architecture"Time is the constraint being tested. Score what exists, coach the pacing.
"Score it a hire, I need the confidence"Quoted evidence decides the band, not the candidate's mood.

References

  • Time budget - minutes per phase at 45 and 60, what must exist, the interrupt lines
  • Rubric - six criteria, 0-3 descriptors, bands, report template
  • Mistakes - symptom, what the coach says, recovery
  • Whiteboard rules - what to sketch per phase, Mermaid conventions, when to render the model answer
  • Problem bank: system-design-case-catalog. Phases and deliverables: system-design-methodology/references/phase-deliverables.md.

© HoangNguyen0403, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (references) in skills/system-design/system-design-interview-coaching of HoangNguyen0403/agent-skills-standard.

  • SKILL.md
  • evals/evals.json
  • references/mistakes.md
  • references/rubric.md
  • references/time-budget.md
  • references/whiteboard-rules.md

Open the folder on GitHubat commit b529c2d

Compare with similar skills

System Design Interview Coaching next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

System Design Interview Coaching compared with similar skills
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System Design Interview Coaching this skillHoangNguyen0403/agent-skills-standard572—~1.3kAutomated safety check: PassMIT
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Mermaid Diagramsjjmartres/opencode1336 repos~1.9kAutomated safety check: PassMIT

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Works with

Categories

Questions about System Design Interview Coaching

What does System Design Interview Coaching do?

Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion…. System Design Interview Coaching is an agent skill from HoangNguyen0403/agent-skills-standard. Runs a timed mock system design round as the interviewer, then scores it as the coach: seven phases on a 45-minute clock, one follow-up on the weakest area, Mermaid sketches in chat, a six-criterion 0-3 rubric with quoted evidence.

When should I use System Design Interview Coaching?

System Design Interview Coaching fits situations like: interview practice; grading a practice design.

How do I install System Design Interview Coaching in Claude Code?

Run `npx skills add HoangNguyen0403/agent-skills-standard --skill system-design-interview-coaching -a claude-code`. Or copy the skill folder (skills/system-design/system-design-interview-coaching in HoangNguyen0403/agent-skills-standard) into .claude/skills/system-design-interview-coaching in your project. Claude Code loads it when a task matches its description.

How do I install System Design Interview Coaching in Codex?

Run `npx skills add HoangNguyen0403/agent-skills-standard --skill system-design-interview-coaching -a codex`. Or copy the skill folder (skills/system-design/system-design-interview-coaching in HoangNguyen0403/agent-skills-standard) into .agents/skills/system-design-interview-coaching in your project. Codex loads it when a task matches its description.

Can I use System Design Interview Coaching in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add HoangNguyen0403/agent-skills-standard --skill system-design-interview-coaching -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/system-design-interview-coaching, .gemini/skills/system-design-interview-coaching, .github/skills/system-design-interview-coaching and .opencode/skills/system-design-interview-coaching in your project.

What does System Design Interview Coaching need to run?

SKILL.md names no scripts, command-line tools or credentials: System Design Interview Coaching is instructions for the agent only.

Does System Design Interview Coaching access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is System Design Interview Coaching safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does System Design Interview Coaching use?

System Design Interview Coaching is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does System Design Interview Coaching use?

About 1.3k tokens (SKILL.md is roughly 5.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 2.4k tokens, read only when the agent opens those files.

What are the alternatives to System Design Interview Coaching?

Skills that share tags, products or a category with System Design Interview Coaching: Archify Diagrams (tt-a1i/archify, 82k stars), Archify Diagram Builder (Unclecheng-li/AI_Animation, 1.5k stars), GitDiagram Repository Overview (ahmedkhaleel2004/gitdiagram, 18k stars) and Code Graph Mermaid Diagrams (trailofbits/skills, 7.5k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains System Design Interview Coaching?

HoangNguyen0403 (a GitHub user) maintains it in HoangNguyen0403/agent-skills-standard, which has 572 GitHub stars. The repository holds 211 skills in this directory. The repository was last updated on October 9, 2026.

Source: HoangNguyen0403/agent-skills-standard on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.