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.
npx agentmods add rules/ekakit/lightfast-mcp/server-extensiongit clone --depth 1 https://github.com/ekakit/lightfast-mcpWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00015 | $0.00477 |
| Opus 5 | $0.00008 | $0.00238 |
| Sonnet 5 | $0.00003 | $0.00095 |
| Haiku 4.5 | $0.00002 | $0.00048 |
Grade A, and why
server-extension 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.
What it actually says
Server Extension Guide
Adding New MCP Servers
1. Create Server Directory Structure
src/lightfast_mcp/servers/{app}/
├── __init__.py
├── server.py # Main server implementation
├── tools.py # Tool implementations
└── resources.py # Resource implementations (optional)
2. Create Entry Point Script
Create src/lightfast_mcp/servers/{app}_mcp_server.py:
@src/lightfast_mcp/servers/mock_server.py
Follow this template pattern, replacing mock with your application name.
3. Add to pyproject.toml
Add new script entry:
[project.scripts]
lightfast-{app}-server = "lightfast_mcp.servers.{app}_mcp_server:main"
4. Server Auto-Discovery
New servers placed in src/lightfast_mcp/servers/{app}/ following the server.py pattern (containing a class that inherits from BaseServer and defines SERVER_TYPE) are automatically discovered by the ServerRegistry located in src/tools/orchestration/server_registry.py. No manual changes to the registry code are typically needed.
5. Add Configuration Support
Update sample configurations to include the new server type
Server Implementation Pattern
from ..core.base_server import BaseServer
from fastmcp import mcp
class {App}MCPServer(BaseServer):
"""MCP server for {App} integration."""
def __init__(self, config):
super().__init__(config)
self.setup_{app}_connection()
@mcp.tool()
async def {app}_tool(self, param: str) -> str:
"""Tool description for AI."""
# Implementation
return "result"
Testing New Servers
- Create unit tests in
tests/unit/test_{app}_server.py - Add integration tests in
tests/integration/test_{app}_integration.py - Include E2E tests if the application supports automation
- Test both stdio and HTTP transports
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.
- 2d ago First seen · 64 lines · 15 tokens per session scan A 02a35717f9dd
server-extension is a cursor rule published in the GitHub repository ekakit/lightfast-mcp (2 stars, last pushed 1y ago), licensed MIT. It adds 15 tokens to every session and 477 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 2026-08-31.
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