# Auto-Generating an Index of Your Claude Code Custom Agents from Their Frontmatter > Source: > Published: 2026-07-29 00:00:06+00:00 This is a continuation of my "Claude Code environment" series. In the previous post, [Automatically thinning conversation logs to prevent bloat](https://zenn.dev/bokuwalily/articles/claude-logs-autodiet), I introduced the basic pattern for scheduled launchd jobs. This time I'm using that same mechanism to **automatically maintain a list of the custom agents in ~/.claude/agents/**. Dropping a single .md file into `~/.claude/agents/` adds a custom agent, but before long you lose track of how many you have, what model each one uses, and which tools each is allowed to touch. That's exactly what happened to me with the 27 agents I now have. I tried writing an INDEX.md by hand to manage them, and of course within a few days it had drifted from reality. Manually updating INDEX.md every time you add a custom agent is not sustainable. `name` or `description` and never noticeI concluded there was no sustainable way to manage this other than "generate it automatically," so I wrote `agents-index.sh` . Here's how the top of my current `~/.claude/agents/INDEX.md` looks. ``` # Agents Index (27 agents · 2026-07-28 02:02) | Name | Model | Description | Tools | |------|-------|-------------|-------| | `architect` ([architect.md](./architect.md)) | opus | Software architecture specialist ... | ["Read", "Grep", "Glob"] | | `build-error-resolver` ([build-error-resolver.md](./build-error-resolver.md)) | sonnet | Build and TypeScript error resolution specialist ... | ["Read", "Write", "Edit", "Bash", "Grep", "Glob"] | | `doc-updater` ([doc-updater.md](./doc-updater.md)) | haiku | Documentation and codemap specialist ... | ["Read", "Edit", "Bash", "Grep", "Glob"] | ``` Four columns: Name, Model, Description, and Tools. You can see at a glance how the models break down across `opus` / `sonnet` / `haiku` , and immediately check things like "did this agent have Bash allowed?" Running it with the `--json` option also writes the same content to `.index.json` , so other scripts like a cost-tracker can reuse it. `~/.claude/scripts/agents-index.sh` is a Bash outer shell with an inline Python3 script embedded in it. ``` bash #!/usr/bin/env bash set -uo pipefail AGENTS_DIR="$HOME/.claude/agents" INDEX_MD="$AGENTS_DIR/INDEX.md" INDEX_JSON="$AGENTS_DIR/.index.json" LOGFILE="$HOME/.claude/logs/agents-index.log" mkdir -p "$HOME/.claude/logs" EMIT_JSON=0 [ "${1:-}" = "--json" ] && EMIT_JSON=1 python3 - "$AGENTS_DIR" "$INDEX_MD" "$INDEX_JSON" "$EMIT_JSON" "$LOGFILE" <<'PY' # ... (Python本体) PY ``` The reason for embedding Python as a heredoc is to hand string processing off to Python while avoiding shell PATH problems. Parsing YAML in pure Bash is dangerous, and assuming `pip install pyyaml` would only add more environment dependencies. Agent definitions only ever use single-level key-value pairs, so a regex plus line splitting is enough. ``` python def load_frontmatter(path): text = path.read_text(encoding="utf-8", errors="replace") m = re.match(r"^---\n(.*?)\n---\n", text, flags=re.DOTALL) if not m: return None, "missing frontmatter" body = m.group(1) out = {} for line in body.split("\n"): if not line.strip() or line.startswith("#"): continue if ":" not in line: continue k, _, v = line.partition(":") k = k.strip() v = v.strip() # quoted string 剥がす if (v.startswith('"') and v.endswith('"')) or (v.startswith("'") and v.endswith("'")): v = v[1:-1] out[k] = v return out, None ``` `re.DOTALL` grabs everything between the `---` markers wholesale, then partitioning on `:` makes everything left of the first `:` the key. JSON array values like `tools` are kept as plain strings and truncated at 60 characters for display. An agent with an empty `name` or `description` is useless even if it shows up in the list. After parsing, the script checks the required fields and appends a warnings section at the end of INDEX.md. ``` if not name: warnings.append(f"{p.name}: missing 'name'") if not desc: warnings.append(f"{p.name}: missing 'description'") ``` The end of the generated output looks like this. ``` ## ⚠️ Validation warnings - foo-agent.md: missing 'description' ``` Note Files that are missing frontmatter entirely get routed to the warnings as`"missing frontmatter"` and don't appear in the table. I designed it to record a warning instead of failing with an error so that INDEX.md generation itself still succeeds while keeping it clear which file is broken. The StartCalendarInterval in `~/Library/LaunchAgents/com.shun.agents-index.plist` looks like this. ``` StartCalendarInterval Hour 6 Minute 30 Weekday 0 ``` `Weekday: 0` is Sunday. The idea is that an up-to-date list is always waiting for me before I start work at the beginning of the week. Process priority is lowered three ways: `Nice: 10` + `LowPriorityIO: true` + `ProcessType: Background` . Index generation involves disk I/O, but lowering the priority of the work keeps it from affecting Claude Code's own responsiveness. Loading is a one-time `launchctl load` . ``` launchctl load ~/Library/LaunchAgents/com.shun.agents-index.plist ``` If you want to run it right now by hand, just call it directly. ``` ~/.claude/scripts/agents-index.sh --json # → agents=27 warnings=0 → ~/.claude/agents/INDEX.md ``` `if p.name == "INDEX.md": continue` . Forget it and INDEX ends up reading INDEX and breaking`|` in a description breaks the table`.replace("|", "\\|")` after parsing. It's in the real code, but I forgot it at first`tools` arrives as a JSON array string, so it easily exceeds the 60-character limit`["Read", "Write", "Edit", "Bash", "Grep", "Glob"]` is already close to 50 characters. Mixing in MCP tools overflows immediately, so truncation + `...` is essential`>>` redirect in ProgramArguments in the plist gives you duplicate logs`pmset -a wake 1` `~/.claude/agents/` grows, a manually maintained INDEX.md is guaranteed to rot → automate the generation`.index.json` `Weekday: 0 / Hour: 6 / Minute: 30` runs it automatically at 6:30 on Sundays. `Nice: 10` + `LowPriorityIO` keeps it out of your way`agents-index.sh --json` Next time, I plan to write about a mechanism that uses this agent list to visualize cost trends per model. *Written by **Lily** — I ship iOS apps and automate my content stack with Claude Code. Follow along: [Portfolio](https://bokuwalily.com) · [X](https://x.com/bokuwalily) · [GitHub](https://github.com/bokuwalily)*