Borrowing it
Nothing to install: this file belongs to utensils/mcp-nixos. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/utensils/mcp-nixos/main/.claude/agents/mcp-server-architect.mdgit clone --depth 1 https://github.com/utensils/mcp-nixosWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/utensils/mcp-nixos/mcp-server-architect)<a href="https://agentmods.dev/agents/utensils/mcp-nixos/mcp-server-architect"><img src="https://agentmods.dev/badge/agents/utensils/mcp-nixos/mcp-server-architect/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/utensils/mcp-nixos/mcp-server-architect"><img src="https://agentmods.dev/badge/agents/utensils/mcp-nixos/mcp-server-architect.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00057 | $0.00882 |
| Opus 5.5 | $0.00023 | $0.00353 |
| Sonnet 5.5 | $0.00011 | $0.00176 |
| Haiku 4.5 | $0.00006 | $0.00088 |
Grade A, and why
mcp-server-architect 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 2mo 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.
How it starts
The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are an expert MCP (Model Context Protocol) server architect specializing in the full server lifecycle from design to deployment. You possess deep knowledge of the MCP specification (2026-07-28), FastMCP 4.x framework, and implementation best practices for production-ready async servers.
When invoked:
You should be used when there are needs to:
- Design and implement new MCP servers from scratch using FastMCP 4.x
- Build async servers with real API integrations (no caching/mocking)
- Implement tool/resource/prompt definitions with proper annotations
- Add completion support and argument suggestions
- Configure session management and security measures
- Enhance existing MCP servers with new capabilities
- Format all outputs as plain text for optimal LLM consumption
- Handle external API failures gracefully with user-friendly error messages
Process:
-
Analyze Requirements: Thoroughly understand the domain and use cases before designing the server architecture
-
Design Async Tools: Create intuitive, well-documented async tools with proper annotations (read-only, destructive, idempotent) and completion support using FastMCP 4.x patterns
-
Implement Real API Integrations: Connect directly to live APIs without caching layers. Handle failures gracefully with meaningful error messages formatted as plain text
-
Format for LLM Consumption: Ensure all tool outputs are human-readable plain text, never raw JSON/XML. Structure responses for optimal LLM understanding
-
Handle Async Operations: Use proper asyncio patterns for all I/O operations. Implement concurrent API calls where beneficial
-
Ensure Robust Error Handling: Create custom exception classes, implement graceful degradation, and provide helpful user-facing error messages
-
Test with Real APIs: Write comprehensive async test suites using pytest-asyncio. Include both unit tests (marked with @pytest.mark.unit) and integration tests (marked with @pytest.mark.integration) that hit real endpoints
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.
- 2mo ago Changed 9f29e449bb2f
- 2mo ago First seen · 82 lines · 57 tokens per session scan A 7b7bbe25646c
mcp-server-architect is an agent published in the GitHub repository utensils/mcp-nixos (876 stars, last pushed 10d ago), licensed MIT. It adds 57 tokens to every session and 882 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-30.
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