pctx

Name: pctx
Author: portofcontext

Pending

pctx is the execution layer for agentic tool calls. It auto-converts agent tools and MCP servers into code that runs in secure sandboxes for token-efficient workflows.

256stars

30forks

Rust

Added 12/27/2025

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AI Agentsai-agentsapiinfrastructurelocal-developmentmcp

Installation

# Add to your Claude Code skills
git clone https://github.com/portofcontext/pctx

Getting Started

Guides for using ai agents skills like pctx.

Caveman: Cut Claude Token Use by 65%
How agent-side prompt compression works, when to use it, and when not to.
What is an AI Skills Marketplace?
Definitions, how marketplaces work, and how to choose between them in 2026.
Getting Started with AI Skills

README.md

Agentic AI for Beginners

Build your first AI agent from scratch - tool use, ReAct pattern, memory, deployment

41 minBeginner

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Install

# Homebrew
brew install portofcontext/tap/pctx

# cURL
curl --proto '=https' --tlsv1.2 -LsSf https://raw.githubusercontent.com/portofcontext/pctx/main/install.sh | sh

# npm
npm i -g @portofcontext/pctx

Core Functionality

pctx can be run as a stateless HTTP server for Code Mode sessions or as a unified MCP server that exposes Code Mode functionality for registered upstream MCP servers.

# Start Code Mode for Python SDK
pctx start

# Start Code Mode as a unified MCP server
pctx mcp init
pctx mcp dev

Python SDK

Use the Python SDK if building agents in Python and want to run Code Mode with custom tools and/or MCP servers. The Python SDK is an HTTP client to the pctx server.

pip install pctx-client

from pctx_client import Pctx, tool
from agents import Agent # Use any Agent SDK
from agents.run import Runner # This example is OpenAI Agents SDK

@tool
def get_weather(city: str) -> str:
    """Get weather information for a given city."""
    return f"It's always sunny in {city}!"

pctx = Pctx(tools=[get_weather]) # or with mcp: servers=[your_mcp]

tools = pctx.openai_agents_tools() # Run Code Mode with any Agent SDK
agent = Agent(
    name="GreatCoder",
    model="litellm/openrouter/openai/gpt-oss-120b",
    instructions="You run code to complete complex tasks.",
    tools=tools,
)

Node SDK

Coming soon

Unified MCP

Use the unified MCP to run Code Mode with MCP servers and want to persist the authentication connections and you do not need to use agent tools (non-mcp tools).

# Initialize config for upstream mcp connections
pctx mcp init

# Add HTTP or stdio MCP servers
pctx mcp add stripe https://mcp.stripe.com
pctx mcp add memory --command "npx -y @modelcontextprotocol/server-memory"

# Start as HTTP server (dev mode with UI)
pctx mcp dev

# Or start as stdio MCP server
pctx mcp start --stdio

For complete CLI documentation, see CLI.md. For configuration options, see Configuration Guide.

What is pctx?

pctx sits between AI agents and MCP servers. It aggregates multiple upstream MCP servers, handles authentication, and exposes tools through a unified Code Mode interface. Instead of agents managing connections to individual MCP servers, they connect once to pctx.

What is Code Mode?

Code mode replaces sequential tool calling with code execution. Rather than an agent calling tools one at a time and passing results through its context window, it writes code that executes in a sandbox. Read Anthropic's overview here.

Traditional MCP flow:

Agent calls getSheet(id)
Server returns 1000 rows → agent's context
Agent calls filterRows(criteria)
Server returns 50 rows → agent's context

With Code Mode:

const sheet = await gdrive.getSheet({ sheetId: "abc" });
const orders = sheet.filter((row) => row.status === "pending");
console.log(`Found ${orders.length} orders`);

Result: 98.7% reduction in tokens (150k → 2k) for this multi-step operation.

Features

Code Mode interface: Tools exposed as code functions for efficient agent interaction. See Code Mode Guide.
Upstream MCP server aggregation: Connect to multiple MCP servers through a single interface, with persistent upstream sessions across execute_typescript calls. See Upstream MCP Servers Guide.
Simple config with CLI: Create the pctx.json config with a simple CLI. pctx.json manages auth, upstream MCPs, logging, and more. See Config Guide.
Secure authentication: Source secrets from environment variables, system keychain, and external commands. See Authentication Section in the CLI configuration docs for more details.

Security

LLM generated code runs in an isolated Deno sandbox that can only access the network hosts specified in the configuration file.
No filesystem, environment, network (beyond allowed hosts), or system access.
MCP clients are authenticated in pctx. LLMs can never see your auth.

Update

Depending on the installation method (Homebrew/npm/cURL) the update method is different. Run which pctx if you are unsure what you used to install it.

# Homebrew update
brew upgrade pctx

# cURL update
pctx-update

# npm update
npm upgrade -g @portofcontext/pctx

Develop

For core dev: install rust and jump into crates/
Client SDK dev: find the README in the SDK