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 skills/alonf/mcppythondemo/mcp-stdio-parity-testingnpx skills add alonf/MCPPythonDemo --skill mcp-stdio-parity-testinggit clone --depth 1 https://github.com/alonf/MCPPythonDemoWhat 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 | $0.00000 | $0.00286 |
| Opus 5 | $0.00000 | $0.00143 |
| Sonnet 5 | $0.00000 | $0.00057 |
| Haiku 4.5 | $0.00000 | $0.00029 |
Grade A, and why
mcp-stdio-parity-testing 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
MCP STDIO Parity Testing Skill
When to use
Use this pattern when a repo needs reviewer-grade validation for:
- a Python MCP stdio server
- a lecture/demo parity path against another reference implementation
- a client-side LLM workflow that should fail cleanly when credentials are missing
Pattern
-
Validate the server with the official SDK client
- start the server with
StdioServerParameters - run
initialize - assert tool discovery
- call the target tool on happy path
- call an invalid tool and confirm an error payload, not a crash
- start the server with
-
Add negative-path unit coverage around live system reads
- patch
/procreaders - require zero/fallback payloads instead of exceptions
- patch
-
Split client validation into two lanes
- fake-model/unit lane for deterministic tool-calling orchestration
- real CLI lane with credentials stripped so missing-config messaging is tested exactly as users see it
-
Make smoke output human-readable
- print the live server payload
- print the validated client failure message
- keep transport details out of the final QA summary
Files in this repo that follow the pattern
tests/test_m1_smoke.pytests/test_system_info.pytests/test_client.pyscripts/smoke_test.py
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 · 39 lines · 0 tokens per session scan A 18a36d6855fb
mcp-stdio-parity-testing is a skill published in the GitHub repository alonf/MCPPythonDemo (0 stars, last pushed 4mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 286 tokens. 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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