What is mcplexer AGENTS.md?

Repository instructions for MCPlexer, a lightweight proxy that lets multiple labeled copies of the same MCP server run together by prefixing their tool names.

Developing, testing, building, and maintaining the MCPlexer proxy.

They document the project structure, commands, connection types, and rules needed to maintain the proxy safely.

How OzTamir/mcplexer configures Codex and OpenCode

Reuse

Borrowing it

Nothing to install: this file belongs to OzTamir/mcplexer. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/OzTamir/mcplexer/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/OzTamir/mcplexer

Made for: Codex, OpenCode.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/oztamir/mcplexer/agents-md/github.svg)](https://agentmods.dev/instructions/oztamir/mcplexer/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/oztamir/mcplexer/agents-md"><img src="https://agentmods.dev/badge/instructions/oztamir/mcplexer/agents-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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/oztamir/mcplexer/agents-md"><img src="https://agentmods.dev/badge/instructions/oztamir/mcplexer/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 729 This file is loaded in full into every session.

When invoked 729 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00729	$0.00729
Opus 5.5	$0.00292	$0.00292
Sonnet 5.5	$0.00146	$0.00146
Haiku 4.5	$0.00073	$0.00073

Measured 2mo ago against content hash 3cfb94a88543, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcplexer AGENTS.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.

AGENTS.md · 70 lines

How it starts

The opening of the file, as written. The whole thing — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCPlexer Agent Guide

Project purpose

MCPlexer is a lightweight stdio MCP proxy. It lets users run multiple labeled instances of the same upstream MCP server by rewriting exposed tool names and descriptions while forwarding calls to the original upstream tool.

Example behavior:

upstream tool: get-calendar-events
exposed tool: personal:get-calendar-events
forwarded call: personal:get-calendar-events -> upstream get-calendar-events

Commands

Use pnpm for package management.

Install: pnpm install
Lint/format check: pnpm lint
Typecheck: pnpm typecheck
Test: pnpm test
Build: pnpm build

Do not run a dev server; this is a CLI/MCP stdio utility.

Architecture map

src/cli.ts: executable boundary, error-to-exit handling.
src/config.ts: public CLI parse orchestration.
src/raw-cli.ts: raw argv tokenization and option parsing.
src/upstream-config.ts: stdio/remote upstream and header config shaping.
src/config-types.ts: shared config types and usage errors.
src/prefix.ts: pure tool-name and description rewrite helpers.
src/upstream.ts: upstream MCP client connection logic for stdio, Streamable HTTP, and SSE.
src/transport-adapter.ts: compatibility adapter for MCP SDK transport typing under exactOptionalPropertyTypes.
src/proxy.ts: downstream stdio MCP server handlers for tools/list and tools/call.
tests/fixtures/echo-mcp.mjs: real upstream MCP fixture for smoke/manual protocol checks.

Invariants

MCPlexer itself always speaks stdio to the downstream client.
Local upstream MCPs are launched with -- <command> [args...] and inherit the wrapper environment.
Remote upstream MCPs use --url; auto tries Streamable HTTP first, then SSE.
Remote OAuth auth must use the MCP SDK authProvider path, not hand-built Authorization headers.
Browser OAuth must keep auth URLs and callback status on stderr or the browser response; stdout stays MCP JSON-RPC only.
Listed tools must preserve upstream metadata except name and description.
tools/call must reject names that do not start with the configured prefix plus separator.
tools/call must strip only the configured prefix before calling upstream.
Keep prefixing behavior pure and testable in src/prefix.ts.
Validate untrusted CLI input at the boundary; do not pass raw argv deeper than src/raw-cli.ts.

Read the full file on GitHub · 70 lines

Changes

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 · 70 lines · 729 tokens per session scan A 3cfb94a88543

Subscribe to this mod's changes

mcplexer AGENTS.md is an instructions file published in the GitHub repository OzTamir/mcplexer (1 stars, last pushed 4mo ago), licensed MIT. It adds 729 tokens to every session, about $0.0029 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.

mcplexer AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
mcplexer AGENTS.mdOzTamir/mcplexer	Instructions file	1	4mo ago	MIT	A	729	Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	today	MIT	A	7,461	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	5,649	GitHub Copilot
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	today	MIT	A	4,680	Codex, OpenCode
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	3,093	GitHub Copilot
vscode model-prompts.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	2,022	GitHub Copilot

mcplexer: Instructions file for Codex