/dev-docs-fetch

Fetch and cache library documentation via Context7 MCP with auto-detect and smart caching.

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Overview

Fetches real, up-to-date library documentation from Context7 MCP and caches it locally with a 7-day TTL. Tech-agnostic: reads $JAAN_CONTEXT_DIR/tech.md for stack detection or accepts explicit library names as arguments. Callable standalone or from other skills' Phase 1 for context enrichment.

This is the first MCP-powered skill in jaan-to (Phase 7).

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Prerequisites

• Context7 MCP server configured (.mcp.json for Claude Code, ~/.codex/config.toml for Codex — both auto-configured during install)
• Project initialized with /jaan-init
• npx available in PATH (for MCP server installation)

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Usage

/dev-docs-fetch fastapi openai react
/dev-docs-fetch

Input	Behavior
Library names as arguments	Fetch docs for specified libraries
No arguments (with tech.md)	Auto-detect libraries from $JAAN_CONTEXT_DIR/tech.md
No arguments (without tech.md)	Ask user which libraries to fetch

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What It Produces

Files at $JAAN_OUTPUTS_DIR/dev/docs/context7/:

File	Content
{library-name}.md	Cached library documentation with YAML frontmatter

Each file includes metadata:

---
title: FastAPI Documentation
library_id: /tiangolo/fastapi
type: context7-reference
created: 2026-02-22
updated: 2026-02-22
context7_mode: code
topic: null
tags: [context7, fastapi, technical-reference]
source: Context7 MCP
cache_ttl: 7 days
---

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What It Asks

Question	When	Why
Which libraries to fetch	No arguments and no tech.md	Need user input for library list
Specific topics within libraries	Optional	More focused documentation (e.g., "middleware")
Code or info mode	Optional	API references vs architecture concepts
Confirm fetch plan	HARD STOP after cache check	User approves which libraries to fetch/skip
Use stale cache on API failure	When API fails and stale cache exists	Fallback to outdated docs vs no docs

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Two-Phase Workflow

Phase 1 — Analysis (Read-Only)

1. Parses arguments or auto-detects from $JAAN_CONTEXT_DIR/tech.md (#current-stack, #frameworks)
2. Checks cache freshness for each library using Bash-based stat/find (cross-platform macOS/Linux)
3. Reports cache status per library: FRESH (skip), STALE (re-fetch), MISSING (fetch)
4. Presents fetch plan at HARD STOP for approval

Phase 2 — Fetch & Store

1. Resolves library IDs via mcp__context7__resolve-library-id
2. Fetches documentation via mcp__context7__get-library-docs (code/info mode, optional topic)
3. Stores each library doc with YAML frontmatter at $JAAN_OUTPUTS_DIR/dev/docs/context7/{library-name}.md
4. Preserves created date on re-fetch (only updates updated)
5. Reports summary: fetched count, skipped (fresh), errors

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Error Handling

Error	Behavior
Library not found	Offer alternative names, retry or skip
API failure	Fallback to stale cache with user consent
Network timeout	Retry up to 3 times with backoff
Invalid response	Skip and continue with remaining libraries

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Workflow Chain

$JAAN_CONTEXT_DIR/tech.md (auto-detect)
  |
  v
/dev-docs-fetch  (fetch + cache)
  |
  v
/backend-scaffold, /frontend-scaffold, etc.

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Example

Input:

/dev-docs-fetch fastapi sqlalchemy

Output:

Cache Status:
  fastapi     — MISSING → will fetch
  sqlalchemy  — FRESH (2 days old) → skip

Fetching 1 library...

  fastapi: Resolved → /tiangolo/fastapi
  fastapi: Fetched (code mode, 4,200 tokens)

Summary: 1 fetched, 1 skipped (fresh), 0 errors
Cache: jaan-to/outputs/dev/docs/context7/

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Tips

• Keep requests to 3-5 libraries per run (token budget: <10,000 tokens)
• Use specific topics for more relevant docs (e.g., "fastapi middleware" instead of all of FastAPI)
• Run before scaffold skills to enrich their context
• Fresh cache is free — the skill skips cached libraries without any MCP calls
• Cached docs are regular markdown files — read them anytime with any tool

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Related Skills

• /dev-verify - Validate build pipeline and services
• /dev-project-assemble - Wire scaffolds into runnable project
• /backend-scaffold - Generate backend code
• /frontend-scaffold - Generate frontend components

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Technical Details

• Logical Name: dev-docs-fetch
• Command: /dev-docs-fetch
• Role: dev
• Output: $JAAN_OUTPUTS_DIR/dev/docs/context7/
• MCP Required: Context7 (resolve-library-id, get-library-docs)
• Token Budget: <10,000 tokens per execution