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/bowen31337/expressjs_mcp/project-structuregit clone --depth 1 https://github.com/bowen31337/expressjs_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 | $0.00391 | $0.00391 |
| Opus 5 | $0.00196 | $0.00196 |
| Sonnet 5 | $0.00078 | $0.00078 |
| Haiku 4.5 | $0.00039 | $0.00039 |
Grade A, and why
project-structure 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 yesterday.
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
Express MCP Project Structure
This project follows the FastAPI-MCP pattern for TypeScript/Express applications.
Core Architecture
The main entry point is src/index.ts, which exports the ExpressMCP class.
Key Modules:
- src/routeIntrospector.ts - Discovers routes from Express app's
_router.stack - src/inMemoryDispatcher.ts - Executes synthetic requests through middleware chain
- src/schemaResolver.ts - Builds tool schemas from OpenAPI/annotations
- src/mcpServer.ts - HTTP gateway for MCP tools at
/mcp/toolsand/mcp/invoke
Usage Patterns
Mount to existing Express app:
const mcp = new ExpressMCP(app, { mountPath: '/mcp' });
await mcp.init();
mcp.mount('/mcp');
Standalone HTTP gateway:
await mcp.startStandalone({ port: 7878 });
Configuration
- Use package.json with pnpm as package manager
- TypeScript config in tsconfig.json
- Biome for linting/formatting via biome.json
- Vitest for testing via vitest.config.ts
Testing
Tests are in tests/ directory using Vitest. Example: tests/routeIntrospector.test.ts
Examples
Basic usage example in examples/basic/server.ts
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.
- yesterday First seen · 46 lines · 391 tokens per session scan A 1268d8635bab
project-structure is a cursor rule published in the GitHub repository bowen31337/expressjs_mcp (1 stars, last pushed 1y ago), licensed MIT. It adds 391 tokens to every session, about $0.0020 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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