Borrowing it
Nothing to install: this file belongs to NimbleBrainInc/mcp-echo. 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/NimbleBrainInc/mcp-echo/main/CLAUDE.mdgit clone --depth 1 https://github.com/NimbleBrainInc/mcp-echoWrote 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/nimblebraininc/mcp-echo/claude-md)<a href="https://agentmods.dev/instructions/nimblebraininc/mcp-echo/claude-md"><img src="https://agentmods.dev/badge/instructions/nimblebraininc/mcp-echo/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/nimblebraininc/mcp-echo/claude-md"><img src="https://agentmods.dev/badge/instructions/nimblebraininc/mcp-echo/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 | $0.00306 | $0.00306 |
| Opus 5.5 | $0.00122 | $0.00122 |
| Sonnet 5.5 | $0.00061 | $0.00061 |
| Haiku 4.5 | $0.00031 | $0.00031 |
Grade A, and why
mcp-echo 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 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- mcp-bash CLAUDE.md — 86% identical, 4 lines differ
What it actually says
Echo MCP Server
FastMCP echo server for testing MCP connections.
Commands
make test # Unit tests
make test-e2e # E2E tests (requires Docker + mcpb CLI)
make check # Format + lint + typecheck + unit tests
make bump VERSION=x.y.z # Bump version in all files
E2E Tests
e2e/ contains end-to-end tests that build and deploy the actual MCPB bundle in a Docker container, then verify health, tool listing, and tool invocation over HTTP.
Prerequisites: Docker running, mcpb CLI installed
The tests automatically vendor Linux-compatible deps (matching the Docker daemon's architecture) using uv pip install --python-platform, so they work on macOS and Linux hosts.
Config: e2e/conftest.py has BASE_IMAGE, PYTHON_VERSION, CONTAINER_PORT, and BUNDLE_NAME.
Release
See mcp-servers/CLAUDE.md for the full release workflow.
make bump VERSION=0.2.0
git add -A && git commit -m "Bump version to 0.2.0"
git tag v0.2.0 && git push origin main v0.2.0
gh release create v0.2.0 --title "v0.2.0" --notes "- changelog"
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 First seen · 34 lines · 306 tokens per session scan A b42933e0b3da
mcp-echo CLAUDE.md is an instructions file published in the GitHub repository NimbleBrainInc/mcp-echo (1 stars, last pushed 3mo ago), licensed MIT. It adds 306 tokens to every session, about $0.0012 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 2026-08-31.
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Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
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AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
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Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
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AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
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Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.