# Context > Context window conservation rules. Invoke when approaching context limits or before large tasks. Use when this capability is needed. - Skill: `tomevault-io/context` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/context` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/context/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/context --- # Context Conservation Rules for maximizing work done per context window. Every token spent on exploration is a token not spent on implementation. ## Core Principles 1. **Grep first, read second** — never Read a file blind. Grep for the symbol/pattern, get line numbers, then Read with offset/limit. 2. **Narrow reads** — always use offset/limit. Aim for 10-20 lines around the target, not 100+. 3. **One read per edit** — Read the target lines, Edit them, move on. Don't re-read to verify; the Edit tool confirms success. 4. **Parallel independent calls** — if you need to read 3 files, do it in one message with 3 Read calls. 5. **No redundant searches** — if you already know the file and line from a prior Grep, go straight to Read+Edit. ## Tool Selection — Cheapest First | Need | Use | NOT | |------|-----|-----| | Find a file by name | `Glob` | Explore agent, `find`, `ls -R` | | Find a symbol in code | `Grep` (files_with_matches) | Explore agent, Read + scan | | Read specific lines | `Read` (offset/limit) | `cat`, `head`, full-file Read | | Simple edit | `Edit` | `sed`, `awk`, Write (full rewrite) | | Repeated pattern edit | `Edit` with `replace_all: true` | Multiple individual Edits | | Add key to 7 i18n files | 7 parallel Edits | Invoke i18n skill | ## When NOT to Use Agents **Don't use Explore/Task agent when:** - You know the file — just Grep + Read directly - The search is simple — one Grep finds it - You need < 3 lookups — do them yourself **Do use Explore agent when:** - Truly open-ended search across unknown files - Need to understand an unfamiliar subsystem - Would take 5+ Grep/Read rounds to find what you need ## When NOT to Invoke Skills **Don't invoke a skill when:** - The task is trivial (e.g., adding one i18n key — just Grep the insertion point and Edit 7 files) - You already know the pattern from memory/context - The skill document is large and the task is small **Do invoke a skill when:** - Following a multi-step procedure with project-specific gotchas - The task is complex enough that the skill's checklist prevents mistakes - You genuinely don't remember the procedure ## Read Discipline ``` BAD: Read(file, offset=1, limit=2000) // entire file, huge context cost BAD: Read(file) // same — default reads everything OK: Read(file, offset=350, limit=50) // 50 lines around target GOOD: Read(file, offset=368, limit=5) // just the lines you need ``` After a Grep gives line 370, read lines 368-373 (offset=368, limit=6). Not 300-450. ## Edit Discipline - **Trust Edit output** — it confirms success. Don't Read after to verify. - **`replace_all: true`** — for patterns repeated across a file (e.g., renaming a variable). One Edit, not N. - **Include minimal context** — `old_string` just needs to be unique, not the whole function. ## Search Strategy 1. Start with `Grep(pattern, output_mode="files_with_matches")` — cheapest, just filenames 2. If needed, `Grep(pattern, output_mode="content", -n=true)` on the specific file — gives line numbers 3. Then `Read(file, offset=line-2, limit=10)` — surgical read 4. Edit and move on ## Multi-File Edits (e.g., i18n) For identical edits across multiple files: 1. Grep one file to find insertion point and context 2. Read the 2-3 target lines from ALL files in parallel (one message, 7 Read calls) 3. Edit ALL files in parallel (one message, 7 Edit calls) Total: 1 Grep + 7 Reads + 7 Edits = 15 tool calls. Not a skill invocation + exploration. ## File Size Awareness Files over ~300 lines cost 1-2K tokens per full read. A read-edit-read cycle on a 1000+ line file eats 4-6K tokens. When a file repeatedly causes context pressure: 1. **Decompose it** — extract inline components, utility functions, tab content into separate files (see `2026-03-03-monster-file-decomposition` journey) 2. **Extraction order**: pure utilities → inline components with typed props → shared/duplicated rendering → tab content → complex sections 3. **Move local-only state into extracted components** — if state is only used within a tab, make it internal, don't pass as props 4. **Target**: each file under 300 lines. The page shell keeps imports, hooks, layout; everything else gets its own file. **Current monster files remaining**: `GovernanceTable.tsx` (1263), `drep/[drepId].tsx` (1392) ## Anti-Patterns | Anti-pattern | Cost | Fix | |---|---|---| | Explore agent for known files | ~50K tokens | Direct Grep + Read | | Full-file Read to find one function | ~5K tokens | Grep for function name first | | Reading file before every Edit | 2x reads | Read once, Edit, trust output | | Loading large skill for small task | ~3K tokens | Just do the task directly | | Re-reading after successful Edit | Wasted read | Edit tool already confirms | | Sequential reads that could be parallel | Wasted turns | Batch into one message | --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/nomos-guild) — claim your Tome and manage your conversions.