mcpx

mcpx is a command line tool that turns registered MCP servers into an agent-friendly command surface.

It keeps MCP server registrations in a global user registry, discovers tool schemas, handles OAuth where possible, and exposes each MCP server as a root command:

mcpx posthog projects-get
mcpx sentry search-issues --input '{"query":"is:unresolved"}'

mcpx is designed for agents. The command surface is intentionally schema-first, stable, and explicit: tool calls pass input through --input, while mcpx's own control commands live under the @ namespace.

Requirements

• Bun
• macOS, Linux, or any environment that can run Bun executables

Install

Install the latest release:

curl -fsSL https://raw.githubusercontent.com/celados/mcpx/main/install.sh | bash

By default, the installer downloads the executable JS bundle from GitHub Releases and installs it to ~/.local/bin/mcpx.

Set MCPX_INSTALL_DIR to choose another install directory.

Add MCP Servers

Register MCP servers globally:

mcpx @add --name posthog --url https://mcp.posthog.com/mcp
mcpx @add --name sentry --url https://mcp.sentry.dev/mcp
mcpx @add --name cf-docs --url https://docs.mcp.cloudflare.com/mcp
mcpx @add --name cf-bindings --url https://bindings.mcp.cloudflare.com/mcp
mcpx @add --name cf-observability --url https://observability.mcp.cloudflare.com/mcp
mcpx @add --name browser --url http://127.0.0.1:9000/mcp

browser-os is an agent-native browser built on Chrome. It exposes a local MCP server that lets agents control the browser directly — navigating pages, extracting content, and interacting with web UIs.

mcpx stores server configuration in:

~/.agents/mcpx/servers.json

OAuth tokens and client secrets are stored separately in the global token cache:

~/.agents/mcpx/tokens.json

Project directories do not need MCP config files. A project should decide which global servers are relevant by using schema selectors or a generated skill.

Call Tools

Call tools through the server command:

mcpx <server> <tool> --input '<json-or-json5>'

Examples:

mcpx posthog projects-get --input '{}'
mcpx sentry whoami --input '{}'

For complex payloads, use @- with a heredoc to keep the input readable:

mcpx cf-graphql graphql_query --input @- <<'JSON'
{
  "query": "query GetWorkerAnalytics($accountTag: String!, $scriptName: String!, $since: Time!, $until: Time!) { viewer { accounts(filter: {accountTag: $accountTag}) { workersInvocationsAdaptive(limit: 1000, filter: {scriptName: $scriptName, datetime_geq: $since, datetime_leq: $until}, orderBy: [datetimeHour_ASC]) { dimensions { datetimeHour scriptName status } sum { requests subrequests errors duration } quantiles { cpuTimeP50 cpuTimeP99 } } } } }",
  "operationName": "GetWorkerAnalytics",
  "variables": {
    "accountTag": "abc123def456",
    "scriptName": "my-worker",
    "since": "2026-04-20T00:00:00Z",
    "until": "2026-04-27T00:00:00Z"
  }
}
JSON

--input is the primary input path. It accepts inline JSON/JSON5, @file, and @- stdin inputs.

Discover Schemas

Print the command schema for agents:

mcpx --schema

Focus on one server:

mcpx --schema=.posthog

Focus on a set of servers:

mcpx --schema='.{posthog,sentry}'

Focus on an internal mcpx command:

mcpx --schema='.["@add"]'

mcpx caches discovered tool schemas in the global registry. Cached schemas older than one day are refreshed opportunistically in a single background worker when mcpx starts, so normal commands do not block on schema discovery. Servers that have not discovered any tools yet are still retried synchronously during startup.

Control Commands

mcpx control commands use the @ namespace so they do not collide with server names:

mcpx @add --name <server> --url <mcp-url>
mcpx @add --name <server> --url <mcp-url> --bearer env:<TOKEN_ENV>
mcpx @add --name <server> --transport stdio --command <command> --args <arg>
mcpx @remove --name <server>
mcpx @refresh
mcpx @daemon status
mcpx @daemon stop
mcpx @daemon server
mcpx @skill

Server names cannot start with @.

HTTP is the default transport. Pass bearer credentials with repeatable --bearer values. env:NAME reads a token from an environment variable at runtime; literal values are accepted but are stored in the registry:

mcpx @add --name posthog --url https://mcp.posthog.com/mcp --bearer env:POSTHOG_TOKEN
mcpx @add --name posthog --url https://mcp.posthog.com/mcp \
  --bearer env:POSTHOG_TOKEN_A \
  --bearer env:POSTHOG_TOKEN_B

Multiple bearer credentials use round-robin selection by default. Stdio servers are local process registrations; pass each process argument with --args, or use --input when you need structured args / env:

mcpx @add --input '{
  "name": "open-design",
  "transport": "stdio",
  "command": "node",
  "args": ["/path/to/open-design/apps/daemon/dist/cli.js", "mcp"],
  "env": { "OPEN_DESIGN_TOKEN": "..." }
}'

@refresh checks every registered MCP server, repairs OAuth state first, refreshes cached tool schemas after auth is ready, and reports servers that still require re-authentication. It may open a browser for interactive OAuth.

Stdio servers are called through mcpxd, a user-local daemon that reuses stdio MCP sessions across CLI invocations. mcpxd starts on demand, keeps idle stdio servers warm, and can be inspected or stopped with mcpx @daemon status and mcpx @daemon stop. The daemon process is started through the explicit mcpx @daemon server subcommand. HTTP servers continue to use the direct client path.

Authentication

Bearer auth is configured explicitly with --bearer. Prefer env:NAME references so secrets stay out of the registry. ${NAME} is also accepted when passed through the shell literally, for example --bearer '${POSTHOG_TOKEN}'. When several bearer credentials are registered, mcpx advances a local round-robin cursor before each HTTP request.

When @add detects OAuth, mcpx tries to complete authentication immediately. For OAuth servers that support dynamic client registration, mcpx registers a client automatically.

For OAuth servers that do not support dynamic client registration, such as Slack, mcpx prompts for a manual client_id and client_secret. These providers usually require a preconfigured redirect URL. mcpx uses:

http://127.0.0.1:65245/callback

Add and save that exact Redirect URL in the provider app settings before continuing the prompt.

When an OAuth token is close to expiry, mcpx refreshes it before calling the MCP tool and then continues the original command.

Tool calls use a 5 minute request timeout by default. Set MCPX_TOOL_CALL_TIMEOUT_MS when a remote MCP server legitimately needs longer.

mcpx buffers MCP subscription notifications and returns them with the next daemon tool-call result by default. Set MCPX_NOTIFICATION_MODE=discard to ignore those notifications for a command; accepted values are buffer and discard.

Output

mcpx optimizes output for humans and agents by default:

• text MCP content is printed directly
• JSON text content is rendered as YAML
• non-text content is saved to a temporary file and printed as file saved <path>
• supplemental MCP structuredContent is printed as $structured only when it is not already represented by the primary content

Use --raw to preserve raw server text output:

mcpx posthog projects-get --raw

Project Skills

Generate a project-local skill that tells agents which global MCP servers to use:

mcpx @skill --servers posthog,sentry

This writes:

.agents/skills/mcpx/SKILL.md

The generated skill instructs agents to discover tools with focused schema selectors and call MCP tools through mcpx.

For temporary agent guidance without writing .agents/skills, print a one-server skill to stdout:

mcpx @skill --show slack

Skill

General mcpx skill definition lives at skills/mcpx/SKILL.md.

License

MIT