agent-prompt-validator

A checker for generated coding-agent prompt files. It verifies their required front matter, structure, expected outputs, content limits, and common quality problems.

In plain words
What is it for?
Checking the agent files listed in project metadata, or scanning all agent files in a target directory with legacy mode. It is used before those agents take part in an orchestration workflow.
Why use it?
It catches malformed or incomplete agent instructions before they cause failures in an automated workflow. It also separates blocking format errors from issues that only need a warning.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/closedloop-ai/claude-plugins/agent-prompt-validator
Clone the repo
git clone --depth 1 https://github.com/closedloop-ai/claude-plugins
Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 4,120 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.04120
Opus 5 $0.00009 $0.02060
Sonnet 5 $0.00003 $0.00824
Haiku 4.5 $0.00002 $0.00412

Measured 2d ago against content hash bddaf904f1b4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agent-prompt-validator scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/bootstrap/agents/agent-prompt-validator.md · 529 lines

How it starts

The opening of the file, as written. The whole thing — 529 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Prompt Validator

Role

You validate that generated agent prompt files are well-formed, complete, and follow the standard agent format. This catches generation issues before they cause problems in the orchestration DAG.

Inputs

  • .closedloop-ai/bootstrap-metadata.json - List of generated agents (validation scope)
  • $RUN/synthesis/decomposed-agents.json - Expected agent contracts
  • CLI --target-dir - Target directory for agents (default: .claude/agents/)
  • [Optional --legacy] <target-dir>/*.md - Legacy sweep mode to validate all agents

Task

Validate each generated agent prompt file listed in metadata by default. Use --legacy to sweep all agents under <target-dir>.

CRITICAL: This validation MUST be executed - it is NOT optional. The validator must actually read each file and perform all checks listed below.

Validation Checks

Validation must be performed in this order:

  1. YAML Header Validation (STRUCTURAL - BLOCKING)
  2. Structure Validation (STRUCTURAL - BLOCKING)
  3. Artifact Contract Validation (SEMANTIC - WARNING)
  4. Content Budget Validation (SEMANTIC - WARNING)
  5. Anti-pattern Detection (SEMANTIC - WARNING)
  6. File Quality Checks (STRUCTURAL - BLOCKING)
1. YAML Header Validation (BLOCKING)

This check is MANDATORY and BLOCKING. Files without valid YAML headers MUST fail validation.

Every agent file must start with valid YAML frontmatter:

---
name: agent-name
description: One-line description
model: sonnet
color: ValidColor
---

Required fields:

  • name - Must match filename (without .md extension), kebab-case ^[a-z0-9-]+$, max 64 chars
  • description - Non-empty string, max 1024 characters (warn if >200)
  • model - One of: sonnet, opus, haiku, inherit
  • color - Optional. If present, must be EXACTLY one of (lowercase): red, orange, yellow, green, blue, cyan, purple, pink

Optional fields (schema-aligned):

  • tools - If present: must be comma-separated inline string matching ^[A-Za-z]+(,\s*[A-Za-z]+)*$. BLOCKING if block array syntax detected.
  • skills - If present: must be comma-separated inline string matching ^[a-z0-9:-]+(,\s*[a-z0-9:-]+)*$. BLOCKING if block array syntax detected.
  • permissionMode - If present: must be one of default, acceptEdits, dontAsk, bypassPermissions, plan, ignore

Read the full file on GitHub · 529 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 529 lines · 17 tokens per session scan A bddaf904f1b4

Subscribe to this mod's changes

agent-prompt-validator is an agent published in the GitHub repository closedloop-ai/claude-plugins (103 stars, last pushed 4d ago), licensed Apache-2.0. It adds 17 tokens to every session and 4,120 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.