Skill Usage Logger Skill

Skill Usage Logger

Overview

Provide a single logger script that any skill can call to append an NDJSON event to ~/.codex/skill-usage.ndjson, with concurrency-safe writes.

Quick Start

Add a small logging note at the very top of a skill's SKILL.md so it is executed whenever that skill runs.
Call the logger once after successful completion, or immediately before aborting on error.

Use this snippet (edit <skill_name> and optional <meta_json>):

# Usage logging (call on success or error as appropriate)
~/.codex/skills/skill-usage-logger/scripts/log_skill_usage.sh \
  --skill "<skill_name>" \
  --status "success" \
  --meta '<meta_json>'

If an error prevents completion, call with --status error and include useful --meta (e.g., reason or failing step).

Logger Script

Path: ~/.codex/skills/skill-usage-logger/scripts/log_skill_usage.sh
Required args:
- --skill <skill_name>
- --status <success|error>
Optional args:
- --meta <json_string> (must be valid JSON; included as meta in the event)

Output format (NDJSON)

Each call appends one line with at least:

{ "ts": "<ISO8601>", "skill": "<skill_name>", "status": "success|error" }

When --meta is provided and valid JSON, it is included as "meta": <json_value>.

Concurrency Notes

The script uses flock on ~/.codex/skill-usage.ndjson.lock to prevent interleaving when multiple skills log at the same time.

Example

~/.codex/skills/skill-usage-logger/scripts/log_skill_usage.sh \
  --skill "frontend-design" \
  --status "success" \
  --meta '{"project":"landing-page","durationMs":1842}'

Resources

scripts/

log_skill_usage.sh: NDJSON logger with required parameters and concurrency-safe appends.

Agent Skills: Skill Usage Logger

Install this agent skill to your local

Skill Files