dunbars-number

dunbars-number is a skill for Claude Code, Codex from deciqAI/knowledge-skills. It costs 115 tokens per session (1,909 once invoked), scanned A, original, MIT.

An organisational framework based on Dunbar's number, the idea that people have limits on how many stable social relationships they can maintain. It describes smaller relationship layers and a commonly cited outer limit of about 150 people.

In plain words
What is it for?
Use it when a team approaches major size milestones, coordination breaks down, startup culture changes, or an organisation is planning offices, sub-units, or acquisition integration.
Why use it?
It helps explain why informal trust and coordination become harder as teams grow. It supports decisions about splitting teams, adding management, or creating separate units.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when a team approaches major size milestones, coordination breaks down, startup culture changes, or an organisation is planning offices, sub-units, or acquisition integration.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/deciqai/knowledge-skills/dunbars-number
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 deciqAI/knowledge-skills --skill dunbars-number
Clone the repo
git clone --depth 1 https://github.com/deciqAI/knowledge-skills

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.

agentmods badge for dunbars-number

README.md
[![agentmods](https://agentmods.dev/badge/skills/deciqai/knowledge-skills/dunbars-number/github.svg)](https://agentmods.dev/skills/deciqai/knowledge-skills/dunbars-number)
Your own site
<a href="https://agentmods.dev/skills/deciqai/knowledge-skills/dunbars-number"><img src="https://agentmods.dev/badge/skills/deciqai/knowledge-skills/dunbars-number/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 dunbars-number

Your own site · 80×15
<a href="https://agentmods.dev/skills/deciqai/knowledge-skills/dunbars-number"><img src="https://agentmods.dev/badge/skills/deciqai/knowledge-skills/dunbars-number.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 115 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,909 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 warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 106
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00115 $0.01909
Opus 5 $0.00057 $0.00955
Sonnet 5 $0.00023 $0.00382
Haiku 4.5 $0.00012 $0.00191

Measured 8d ago against content hash bbee891df2b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

dunbars-number 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 8d 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.

dunbars-number/SKILL.md · 124 lines

How it starts

The opening of the file, as written. The whole thing — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Dunbar's Number

Overview

Dunbar's number (~150) is the cognitive limit on stable social groups the human neocortex can sustain, with nested layers at ~5, ~15, ~50, then outer bands at ~500 and ~1,500. Derived by Robin Dunbar (1992) from primate neocortex ratios. Key implication: below ~150, informal trust coordinates behavior; above ~150, formal hierarchy becomes architecturally mandatory — not a cultural choice.

Composes with network-effects (different coordination mechanisms below vs. above 150), principal-agent (exceeding 150 multiplies agency problems informal trust can no longer cover), founder-mindset (founder relationship bandwidth peaks at ~150 — first breakpoint demanding shift from doing to delegating structure).

When to Use

  • Headcount approaching or crossing 150 (or 50, or 500)
  • "Coordination getting harder" complaints with no obvious structural cause
  • Deciding to split a team, open a new office, or create a sub-unit
  • Designing org structure for a scaling startup; evaluating acquisition integration plans
  • Diagnosing why informal culture "felt different" after a headcount milestone
  • AI-native startup hiring fast on abundant AI-era capital / AI-adoption demand — "we scaled from 20 to 150 in a year and coordination is breaking"

Not when: group well below 50 and problems are interpersonal; constraint is incentive misalignment (use principal-agent); challenge is growing a network beyond 150 (use network-effects).

Coaching Novices (Adaptive Front Door)

  • Engine mode: user has a concrete org design or headcount question → run The Process directly.
  • Coach mode: user is unfamiliar → guide step by step.

In Coach mode, respond one step at a time. Each [WAIT] is a hard stop — output only that step's question, then stop.

  1. One-liner: once a group exceeds ~150 people, informal trust cannot coordinate it — formal structure is architecturally required by the human neocortex.
  2. Check fit: what is the current headcount? Which Dunbar layer, which breakpoint is approaching?
  3. Elicit the structure: what coordination mechanisms exist? Where are they breaking down?

[WAIT — do not advance until user responds]

  1. Run The Process one step at a time with their input.

[WAIT — do not advance until user responds]

  1. Close: group layer + breakpoint diagnosis + structural prescription (split / formalize / layer) named.

[WAIT — do not advance until user responds]

Read the full file on GitHub · 124 lines

Files

What ships with it

3 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.

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. 8d ago First seen · 124 lines · 115 tokens per session scan A bbee891df2b1

Subscribe to this mod's changes

dunbars-number is a skill published in the GitHub repository deciqAI/knowledge-skills (10 stars, last pushed 10d ago), licensed MIT. It adds 115 tokens to every session and 1,909 once invoked, about $0.0006 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 2026-09-03.

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