🛡️ plan-linter

"Fail your agent's flight-plan in CI—before it fails production."

plan-linter is an open-source static analysis toolkit for LLM agent plans.

It parses the machine-readable plan emitted by a planner/brain, validates it against schemas, policy rules, and heuristics, and returns Pass / Fail with an annotated risk-score JSON.

📦 Installation

Using pip

pip install plan-lint

From source

git clone https://github.com/cirbuk/plan-lint.git
cd plan-lint
pip install -e .

🚀 Quick Start

The simplest way to use plan-linter is to run it on a plan JSON file:

plan-lint path/to/plan.json

For a more advanced usage, you can provide a policy file:

plan-lint path/to/plan.json --policy path/to/policy.yaml

📝 Example Plan Format

{
  "goal": "Update product prices with a discount",
  "context": {
    "user_id": "admin-012",
    "department": "sales"
  },
  "steps": [
    {
      "id": "step-001",
      "tool": "sql.query_ro",
      "args": {
        "query": "SELECT product_id, current_price FROM products"
      },
      "on_fail": "abort"
    },
    {
      "id": "step-002",
      "tool": "priceAPI.bulkUpdate",
      "args": {
        "product_ids": ["${step-001.result.product_id}"],
        "discount_pct": -20
      }
    }
  ],
  "meta": {
    "planner": "gpt-4o",
    "created_at": "2025-05-15T14:30:00Z"
  }
}

📋 Example Policy Format

# policy.yaml
allow_tools:
  - sql.query_ro
  - priceAPI.bulkUpdate
bounds:
  priceAPI.bulkUpdate.discount_pct: [-40, 0]
deny_tokens_regex:
  - "AWS_SECRET"
  - "API_KEY"
max_steps: 50
risk_weights:
  tool_write: 0.4
  raw_secret: 0.5
  loop: 0.3
fail_risk_threshold: 0.8

For detailed information on creating policies, including advanced YAML policies and Rego policies with Open Policy Agent integration, see our Policy Authoring Guide.

🔍 Command Line Options

Usage: plan-lint [OPTIONS] PLAN_FILE

Options:
  --policy, -p TEXT     Path to the policy YAML file
  --schema, -s TEXT     Path to the JSON schema file
  --format, -f TEXT     Output format (cli or json) [default: cli]
  --output, -o TEXT     Path to write output [default: stdout]
  --fail-risk, -r FLOAT Risk score threshold for failure (0-1) [default: 0.8]
  --help                Show this message and exit

🧩 Adding Custom Rules

You can create custom rules by adding Python files to the plan_lint/rules directory. Each rule file should contain a check_plan function that takes a Plan and a Policy object and returns a list of PlanError objects.

Here's an example of a custom rule that checks for SQL write operations:

from typing import List

from plan_lint.types import ErrorCode, Plan, PlanError, Policy

def check_plan(plan: Plan, policy: Policy) -> List[PlanError]:
    errors = []
    
    for i, step in enumerate(plan.steps):
        if step.tool.startswith("sql.") and "query" in step.args:
            query = step.args["query"].upper()
            write_keywords = ["INSERT", "UPDATE", "DELETE"]
            
            for keyword in write_keywords:
                if keyword in query:
                    errors.append(
                        PlanError(
                            step=i,
                            code=ErrorCode.TOOL_DENY,
                            msg=f"SQL query contains write operation '{keyword}'",
                        )
                    )
    
    return errors

🤝 Contributing

We welcome contributions from the community! To get started:

1. Check the open issues or create a new one to discuss your ideas
2. Fork the repository
3. Make your changes following our contribution guidelines
4. Submit a pull request

Please read our Code of Conduct to keep our community approachable and respectable.

🏗️ Development

To set up a development environment:

# Clone the repository
git clone https://github.com/cirbuk/plan-lint.git
cd plan-lint

# Create a virtual environment
python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

# Install development dependencies
pip install -e ".[dev]"

# Install pre-commit hooks
pre-commit install

📚 Documentation

For comprehensive documentation, visit our documentation site or build it locally:

# Clone the repository
git clone https://github.com/cirbuk/plan-lint.git
cd plan-lint

# Create and activate a virtual environment
python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

# Install the package with documentation dependencies
pip install -e ".[docs]"

# Build and serve the documentation locally
mkdocs serve

The documentation includes:

• Detailed guides on policy authoring
• Examples of integrating with MCP servers
• API reference
• Advanced usage scenarios

You can also build a static version of the documentation:

mkdocs build

This will create a site directory with the static HTML documentation.

📄 License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.