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 rules/duckduckgo/apple-browsers/documentation-principlesgit clone --depth 1 https://github.com/duckduckgo/apple-browsersWhat 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 | $0.00011 | $0.00471 |
| Opus 5 | $0.00005 | $0.00235 |
| Sonnet 5 | $0.00002 | $0.00094 |
| Haiku 4.5 | $0.00001 | $0.00047 |
Grade A, and why
documentation-principles 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 today.
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 — 47 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Documentation Principles
Overview
This guide establishes core principles for creating and maintaining project documentation. It covers when to document, where documentation should live based on abstraction level, and how to write valuable documentation.
For DocC syntax and features, see Apple's DocC Documentation.
When to Document
Document when introducing or changing:
- Public APIs - New protocols, methods, or significant behavior changes
- Integration patterns - How features connect or how to use packages
- Complex modules - Non-obvious architecture or usage patterns
Where Documentation Lives
Documentation should live at the same abstraction level as the code it documents:
Package Documentation = Public protocol/API definitions, package architecture, reusable patterns App Documentation = How the app integrates those packages, platform-specific patterns, app-specific protocols
Good Documentation Practices
Security and Privacy: Document architectural concepts, flows, and how systems work. Never document actual secrets, API keys, endpoints, credentials, or any sensitive implementation details that could pose security risks.
✅ Respect abstraction levels - Package docs explain APIs, app docs explain integration ✅ Link, don't duplicate - App docs reference package APIs instead of copying them ✅ Document stable interfaces - Avoid ephemeral details (line numbers, paths, folder structures) ✅ Provide code snippets for non-trivial API usage - Show how to use complex APIs ✅ Document for understanding, not existence - Explain how it works and how to use it, not just that it exists
Bad Documentation Practices
Security and Privacy: Never include actual API endpoints, authentication tokens, encryption keys, internal URLs, credentials, or any information that could compromise security or user privacy.
❌ Mixing abstraction levels - See: Respect abstraction levels ❌ Duplicating content across documentation - See: Link, don't duplicate ❌ Documenting ephemeral details - See: Document stable interfaces ❌ Including trivial code snippets - See: Provide code snippets for non-trivial API usage ❌ Documenting just for existence sake - See: Document for understanding, not existence
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.
- today First seen · 47 lines · 11 tokens per session scan A 6cdcb06a6b89
documentation-principles is a cursor rule published in the GitHub repository duckduckgo/apple-browsers (252 stars, last pushed today), licensed Apache-2.0. It adds 11 tokens to every session and 471 once invoked, about $0.0001 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 2026-09-01.
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