MCP Backpressure MCP Server

Backpressure and concurrency control middleware for [FastMCP](https://github.com/jlowin/fastmcp) MCP servers.

Local serverstdioPython

What is the MCP Backpressure MCP server?

Most developer tooling work still happens through a UI a human drives. MCP Backpressure MCP server moves it into the conversation instead. Backpressure and concurrency control middleware for FastMCP MCP servers.

The short version

  • Concurrency limiting — Semaphore-based control of parallel executions
  • Bounded queue — Optional FIFO queue with configurable size
  • Queue timeout — Automatic timeout for queued requests with cleanup
  • Structured errors — JSON-RPC compliant overload errors with detailed metrics
  • Metrics — Real-time counters for active, queued, and rejected requests
  • Callback hook — Optional notification on each overload event

The tools it exposes

The server publishes 3 tools. What each one is for:

  • Parameters — The Parameters tool exposed by this server
  • Metrics — print(f"Active: {metrics.active}") print(f"Queued: {metrics.queued}") print(f"Total rejected: {metrics.total_rejected}") print(f"Rejected
  • Linting — The Linting tool exposed by this server

Getting it running

Installation goes through your MCP client rather than a global install: point it at mcp-backpressure on PyPI and it is fetched when the client starts. The copy-paste blocks for Claude Desktop, Claude Code and Cursor are further down this page.

How it compares

Among the developer tooling options, the useful question is rarely "what can it do" but "what does it cost you to run" — permissions, credentials, and how much of your context its toolset consumes. MCP Backpressure's toolset — Parameters, Metrics, Linting — is a fair guide to whether it matches your workflow. It is maintained by nulone; worth a glance at recent repository activity before you build anything load-bearing on it.

This entry was verified against MCP Backpressure's own documentation before publication; SyncDev keeps the directory reviewed rather than auto-generated.

Things to watch

  • It runs with your machine's permissions. That is convenient and also the reason to think about what you point it at before you approve a tool call.
  • Keep per-call confirmation enabled while you learn its behaviour; it is the cheapest safeguard you have.

Available tools

ToolWhat it does
ParametersThe Parameters tool exposed by this server.
Metricsprint(f"Active: {metrics.active}") print(f"Queued: {metrics.queued}") print(f"Total rejected: {metrics.total_rejected}") print(f"Rejected (concurrency): {metrics.rejected_concurrency_limit}") print(f"Rejected (queue full
LintingThe Linting tool exposed by this server.

How to install the MCP Backpressure MCP server

{
  "mcpServers": {
    "backpressure": {
      "command": "uvx",
      "args": ["mcp-backpressure"]
    }
  }
}

Add to claude_desktop_config.json, then restart Claude Desktop.

Example prompts to try

  • Use MCP Backpressure to Parameters.
  • Use MCP Backpressure to Metrics.
  • Use MCP Backpressure to Linting.

Frequently asked questions

It connects MCP Backpressure to MCP-compatible AI assistants such as Claude and Cursor, exposing 3 tools (Parameters, Metrics, Linting) that the assistant can call on your behalf. Instead of copying data back and forth by hand, the assistant works with MCP Backpressure directly.