Understand Explain Agent Skill

/understand-explain

Provide a thorough, in-depth explanation of a specific code component.

Graph Structure Reference

The knowledge graph JSON has this structure:

• project — {name, description, languages, frameworks, analyzedAt, gitCommitHash}
• nodes[] — each has {id, type, name, filePath?, summary, tags[], complexity, languageNotes?}
• Code node types: file, function, class, module, concept
• Non-code node types: config, document, service, table, endpoint, pipeline, schema, resource
• Domain/knowledge node types: domain, flow, step, article, entity, topic, claim, source
• IDs use the node type as prefix, e.g. file:path, function:path:name, config:path, article:path
• edges[] — each has {source, target, type, direction, weight}
• Key types: imports, contains, calls, depends_on, configures, documents, deploys, triggers, contains_flow, flow_step, related, cites
• layers[] — each has {id, name, description, nodeIds[]}
• tour[] — each has {order, title, description, nodeIds[]}

How to Read Efficiently

• Use Grep to search within the JSON for relevant entries BEFORE reading the full file
• Only read sections you need — don't dump the entire graph into context
• Node names and summaries are the most useful fields for understanding
• Edges tell you how components connect — follow imports and calls for dependency chains

Instructions

• Resolve the data directory $UA_DIR. Run UA_DIR=$([ -d .understand-anything ] && echo .understand-anything || echo .ua) — this is the legacy .understand-anything/ when it already exists, otherwise the new .ua/. Check that $UA_DIR/knowledge-graph.json exists. If not, tell the user to run /understand first.

• Check graph freshness before using graph-derived context:
• Read project.gitCommitHash from the graph metadata as GRAPH_COMMIT_RAW. Resolve it as a commit before using it in any Git diff, then compare it with git rev-parse HEAD and inspect project-scoped committed and working-tree changes from the project root:

     GRAPH_COMMIT=$(git rev-parse --verify --end-of-options "${GRAPH_COMMIT_RAW}^{commit}" 2>/dev/null)
     git rev-parse HEAD
     git diff --name-only "$GRAPH_COMMIT" HEAD -- .
     git diff --cached --name-only -- .
     git diff --name-only -- .
     git ls-files --others --exclude-standard -- .

• The -- . pathspec is required: commits that only touch a sibling monorepo project must not make this graph stale. A hash mismatch alone is not stale when the project diff is empty.
• Ignore the selected data directory (.ua/ or legacy .understand-anything/) in every command's output because it contains generated graph artifacts, not project source drift.
• If the committed diff or any working-tree command reports project files, warn before explaining that graph-derived context may omit those changes. Suggest: Run /understand to refresh the graph.
• Run the commit diff only when GRAPH_COMMIT_RAW resolves successfully. If the graph commit or Git metadata is missing, invalid, or unavailable, give a brief best-effort warning and continue instead of blocking.

• Find the target node — use Grep to search the knowledge graph for the component: "$ARGUMENTS"
• For file paths (e.g., src/auth/login.ts): search for "filePath" matches
• For function notation (e.g., src/auth/login.ts:verifyToken): search for the function name in "name" fields filtered by the file path
• Note the exact node id, type, summary, tags, and complexity

• Find all connected edges — Grep for the target node's ID in the edges section:
• "source" matches → things this node calls/imports/depends on (outgoing)
• "target" matches → things that call/import/depend on this node (incoming)
• Note the connected node IDs and edge types

• Read connected nodes — for each connected node ID from step 4, Grep for those IDs in the nodes section to get their name, summary, and type. This builds the component's neighborhood.

• Identify the layer — Grep for the target node's ID in the "layers" section to find which architectural layer it belongs to and that layer's description.

• Read the actual source file — Read the source file at the node's filePath for the deep-dive analysis.

• Explain the component in context:
• Its role in the architecture (which layer, why it exists)
• Internal structure (functions, classes it contains — from contains edges)
• External connections (what it imports, what calls it, what it depends on — from edges)
• Data flow (inputs → processing → outputs — from source code)
• Explain clearly, assuming the reader may not know the programming language
• Highlight any patterns, idioms, or complexity worth understanding