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    πŸ“ Prompt Template Linter

    πŸ“ Prompt Template Linter

    by JustHandled Labs

    Lint a prompt template for the issues that cause injection and flaky output. Flags untrusted variables interpolated straight into the instructions (the injection surface), placeholders that are never provided or never used, contradictory instructions, a missing output-format spec where the result is parsed, unbounded context interpolation, and leftover placeholders. It detects problems; it does not write prompts.

    Updated Jun 2026
    Security scanned
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    $12

    Β· or 60 credits

    30-day refund guarantee

    Secure checkout via Stripe

    Included in download

    • Identify prompt injection surfaces in dynamic Jinja2 templates.
    • Fix broken variable references and leftover placeholders before deployment.
    • file_read, terminal automation included
    • Ready for Cursor
    • Instant install

    Sample input

    Lint the prompt templates in the /prompts directory and check for injection risks and missing variables.

    Sample output

    Findings:

    • [PTL001] SEVERE: /prompts/user_gen.j2 (Line 12) - Untrusted variable 'user_input' interpolated into instruction region.
    • [PTL002] WARNING: /prompts/summary.md (Line 4) - Placeholder 'date_range' is defined but never used in the template.

    About This Skill

    What it does

    The Prompt Template Linter is a specialized diagnostic tool designed to sanitize and optimize LLM prompt templates before they reach production. It scans your template files to identify structural flaws, security risks, and logical inconsistencies that often lead to model hallucinations or prompt injection vulnerabilities.

    Why use this skill

    Manually auditing prompts for "jailbreak" surfaces or missing variables is error-prone. This skill automates the detection of critical issues like unescaped user input in instruction blocks, contradictory constraints, and orphaned placeholders. It ensures your prompts are robust, type-safe (where variables are concerned), and formatted for reliable parsing.

    Supported tools

    • File Formats: Supports .prompt, .txt, .md, .jinja, and .j2 files.
    • Integration: Works via CLI or stdin, making it ideal for pre-commit hooks or CI/CD pipelines.
    • Remediation: Includes a library of safe-snippet references to fix flagged issues instantly.

    Output format

    The skill produces a structured report categorized by rule ID (PTL001-PTL006) and severity, pinpointing the exact line and file where the issue resides.

    Use Cases

    • Identify prompt injection surfaces in dynamic Jinja2 templates.
    • Fix broken variable references and leftover placeholders before deployment.
    • Detect contradictory model instructions that lead to hallucinations.
    • Enforce output schema requirements for reliable downstream parsing.

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    Security Scanned

    Passed automated security review

    Permissions

    Read Files
    Terminal / Shell

    File Scopes

    prompt-template-linter/**
    **/*.prompt
    **/prompts/**/*.txt
    **/prompts/**/*.md
    **/*.jinja
    **/*.j2
    --stdin

    Read-only. It is a detector, not a prompt generator. Reads no environment variables and writes nothing.

    Tags

    prompt-engineering
    security
    llm-ops
    jinja2
    linting

    Works with any agent that can read a file and run a local Python script (Claude Code, Cursor, Codex CLI, and other SKILL.md-compatible agents). Standard library only, no install step. Read-only, no network.

    Creator

    JustHandled Labs

    JustHandled Labs builds focused agent skills for the work nobody wants to do by hand. Each one is a single repeatable job done well: catching the security and data mistakes that quietly ship, keeping docs and tests honest, gating the commands an agent is about to run, sharpening writing, and handling the founder chores around launches, outreach, and brand setup. Not generic AI productivity. Specific workflows that are easy to run, review, and repeat. Maintained by H.J. Westerfield, with a background in communications, editing, project coordination, customer support, and practical AI systems. Tools for people who want useful automation without theatrical complexity.

    Frequently Asked Questions

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