Fetch an agent definition from a URL and run claude with it

claude-agent-from-url

#!/usr/bin/env python3
# /// script
# dependencies = []
# ///
"""
Fetch an agent definition from a URL and run claude with it.
"""

import sys
import json
import re
import subprocess


def parse_frontmatter(content):
    """Parse YAML frontmatter from markdown content."""
    # Match content between --- markers
    match = re.match(r"^---\s*\n(.*?)\n---\s*\n(.*)", content, re.DOTALL)

    if not match:
        raise ValueError("No frontmatter found in content")

    frontmatter_text = match.group(1)
    body = match.group(2)

    # Simple YAML parser for our use case
    metadata = {}
    for line in frontmatter_text.split("\n"):
        line = line.strip()
        if ":" in line:
            key, value = line.split(":", 1)
            metadata[key.strip()] = value.strip()

    return metadata, body


def fetch_url(url):
    # Use curl to avoid SSL cert issues
    result = subprocess.run(
        ["curl", "-fsSL", url], capture_output=True, text=True, check=True
    )
    return result.stdout


def build_agent_json(metadata, body):
    """Build the agent JSON structure."""
    name = metadata.get("name", "agent")
    description = metadata.get("description", "")

    agent_config = {name: {"description": description, "prompt": body.strip()}}

    return json.dumps(agent_config)


def main():
    if len(sys.argv) < 2:
        print("Usage: claude-agent <url>", file=sys.stderr)
        print("\nExample:", file=sys.stderr)
        print(
            "  claude-agent https://raw.githubusercontent.com/foo.md",
            file=sys.stderr,
        )
        sys.exit(1)

    url = sys.argv[1]

    # Fetch and parse the agent definition
    print(f"Fetching agent from: {url}", file=sys.stderr)
    content = fetch_url(url)

    metadata, body = parse_frontmatter(content)
    agent_name = metadata.get("name", "agent")

    print(f"Loaded agent: {agent_name}", file=sys.stderr)
    print(f"Description: {metadata.get('description', 'N/A')}", file=sys.stderr)

    # Build the agent JSON
    agent_json = build_agent_json(metadata, body)

    # Construct the claude command
    cmd = [
        "claude",
        # TODO: Replace with more nuanced approach
        "--dangerously-skip-permissions",
        "--agents",
        agent_json,
        "--append-system-prompt",
        f"Use the {agent_name} agent to handle the task.",
    ]

    print("", file=sys.stderr)

    subprocess.run(cmd, check=True)


if __name__ == "__main__":
    main()