Borrowing it
Nothing to install: this file belongs to krish-shahh/mcp-idempotent. 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/krish-shahh/mcp-idempotent/main/CLAUDE.mdgit clone --depth 1 https://github.com/krish-shahh/mcp-idempotentWrote 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/instructions/krish-shahh/mcp-idempotent/claude-md)<a href="https://agentmods.dev/instructions/krish-shahh/mcp-idempotent/claude-md"><img src="https://agentmods.dev/badge/instructions/krish-shahh/mcp-idempotent/claude-md/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/instructions/krish-shahh/mcp-idempotent/claude-md"><img src="https://agentmods.dev/badge/instructions/krish-shahh/mcp-idempotent/claude-md.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 | $0.01943 | $0.01943 |
| Opus 5 | $0.00971 | $0.00971 |
| Sonnet 5 | $0.00389 | $0.00389 |
| Haiku 4.5 | $0.00194 | $0.00194 |
Grade A, and why
mcp-idempotent CLAUDE.md 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 9d 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 — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Spec: MCP Idempotency Proxy
Context / Prior Art
A retried MCP tool call can re-execute a side effect (double charge, duplicate ticket, etc.). This has been checked against the current landscape and is a real, unclaimed gap:
-
MCP core spec: SEP-1686 ("Tasks", Final, Oct 2025) adds an idempotency mechanism, but scoped narrowly to task creation — a client-generated task ID lets the server reject a duplicate with an error, so a retried task-augmented request can't spawn a second task. It says nothing about an ordinary
tools/call, which is the common case (most tool calls aren't tasks). There is also anidempotentHinttool annotation, but it's a static declaration ("this tool happens to be idempotent"), not an enforcement mechanism — nothing in the protocol checks it or acts on it. -
Existing OSS MCP gateways (IBM/mcp-context-forge, microsoft/mcp-gateway, MikkoParkkola/mcp-gateway, aws/mcp-proxy-for-aws): ship auth, rate limiting, observability, and in one case circuit breakers. None ship idempotency-key deduplication of tool calls.
-
DIY precedent: found blog-post-level Redis middleware snippets solving this per-project, for tools a team already owns. No packaged, reusable, transport-level version exists.
(An earlier draft of this doc cited an arXiv paper as "closest prior art" describing caller-supplied idempotency keys for tool calls. That citation was checked against the actual paper and was wrong — the paper exists but covers a different topic entirely. Removed rather than replaced with an unverified substitute.)
The gap, specifically: an open-source, MCP-transport-aware proxy that adds idempotency-key deduplication generically, in front of any existing, unmodified MCP server. That combination doesn't exist yet.
Objective
A retried MCP tool call should never re-execute a side effect. This proxy
sits transparently in front of any existing, unmodified MCP server and adds
Stripe-style idempotency-key deduplication to tools/call. If the same
logical call is seen twice, the second call returns the cached result instead
of hitting the tool again.
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.
- 9d ago First seen · 157 lines · 1,943 tokens per session scan A 5662b1ab0d38
mcp-idempotent CLAUDE.md is an instructions file published in the GitHub repository krish-shahh/mcp-idempotent (0 stars, last pushed 1mo ago), licensed MIT. It adds 1,943 tokens to every session, about $0.0097 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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