git:20260628.a73ddcc to git:20260813.9eff097

---

name: mcpx

description: Use when the user needs to discover or call already-configured MCP servers through the mcpx CLI, including generating project-local MCP routing skills.

---

# mcpx

`mcpx` turns registered MCP servers into an agent-friendly command surface.

Use it when a task needs MCP-backed services such as PostHog, Sentry, Cloudflare,

or another server registered in the user's global mcpx registry.

## Execution Rules

- Run `mcpx` directly.

- Start with the server inventory instead of dumping every registered schema.

- Call MCP tools as `mcpx <server> <tool> --input <json>`.

- Pass all tool arguments through `--input`; do not invent flags for MCP tool fields.

- Use focused schema selectors before calling tools on large MCP surfaces.

- Do not hand-edit `~/.agents/mcpx/servers.json` or token cache files unless the user explicitly asks for registry surgery.

- Treat MCP server registration and OAuth setup as human-owned configuration. If a required server is missing or unauthenticated, stop and ask the user to configure it.

## First Move: Discover The Surface

At the start of an MCP task, run bare `mcpx` to list configured servers:

```bash

mcpx

```

Choose the likely server from the user's request, then inspect only that server's

schema:

```bash

mcpx --schema=.sentry

mcpx --schema=.posthog

```

After that, narrow to the specific tool or a short candidate list:

```bash

mcpx --schema=.posthog.projects-get

mcpx --schema='.posthog.{projects-get,alerts-list,alert-create}'

```

Avoid `mcpx --schema` unless the user explicitly asks for the complete command

surface. On a real registry it may expand every server schema and waste the

agent context.

## Call Tools

Use inline JSON/JSON5 for tiny inputs:

```bash

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

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

```

For non-trivial payloads, prefer `@file` or heredoc input:

```bash

mcpx <server> <tool> --input @payload.json

mcpx <server> <tool> --input @- <<'JSON'

{

"query": "is:unresolved"

}

JSON

```

Default output is optimized for agents (YAML for structured content,

direct text passthrough, media saved as `file saved <path>`). Use `--raw` to

disable that optimization. When a tool emits notifications, `--raw` output may

also include a JSON envelope — see Notifications below.

## Server Transports

mcpx supports two MCP transports, both configured through `mcpx @add`:

- **HTTP** — default. Remote MCP services like PostHog or Sentry.

- **Stdio** — local processes started by mcpx, for example

`mcpx @add --name fs --transport stdio --command bunx --args -y --args @modelcontextprotocol/server-filesystem --args /tmp/fs-sandbox`.

HTTP bearer auth uses `--bearer`. Prefer `env:NAME` so secrets stay out of the

registry. Repeat `--bearer` for multiple credentials; mcpx uses round-robin by

default:

```bash

mcpx @add --name posthog --url https://mcp.posthog.com/mcp \

--bearer env:POSTHOG_TOKEN_A \

--bearer env:POSTHOG_TOKEN_B

```

After registration both behave identically from the agent's view: same schema

discovery, same `mcpx <server> <tool> --input ...` call pattern, same output

shape. You do not need to differentiate when calling tools.

## Notifications

Most tools emit no notifications and this section never applies.

When an MCP server emits events during a call (progress reporting, server-side

state changes, custom events), mcpx merges them into default structured output

under an injected `$notifications` field:

```yaml

count: 1

$notifications:

- method: notifications/progress

params:

progressToken: '...'

progress: 3

total: 4

message: step 3

```

For non-JSON text, binary, or mixed content, mcpx falls back to the trailing

sentinel line:

```

<tool result lines>

$notification: [{"method":"notifications/progress","params":{...}}]

```

Notifications are objects with these fields:

- `method` — MCP notification method name

- `params` — method-specific payload (shape depends on `method`)

- `aggregatedCount` — only on the **last** `notifications/progress` entry per

progress token; indicates that N intermediate progress entries were collapsed

to keep output bounded. The first and last entries are preserved verbatim.

Notification methods you may encounter:

| method | meaning |

| ------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |

| `notifications/progress` | Progress for a long-running tool. Carries `{ progressToken, progress, total?, message? }`. |

| `notifications/tools/list_changed` | Server's tool schema changed. mcpx automatically refreshes the registry; you do not need to react. |

| `$oversize` | Synthetic raw-mode marker. Means notifications were saved to a temp JSON file. Default output renders this as `notifications oversize, saved to <path>`. |

| other (e.g. `notifications/custom/*`) | Passed through verbatim. Server-specific. |

In `--raw` mode with a structured result and non-empty notifications, the

trailing sentinel line is replaced by a JSON envelope on stdout:

```json

{ "result": <tool-result>, "notifications": [ ... ] }

```

Text results keep the trailing `$notification:` line even under `--raw`,

because text content is not JSON and wrapping it would break consumers.

Practical guidance:

- If your task does not depend on progress or server events, ignore notifications.

- Check `$notifications`, the sentinel line, or the raw envelope only when present.

- Do not assume notifications appear; the common case is no `$notification:` at all.

## Project-Local Skills

When the user has already configured the relevant global MCP servers and wants a

project to expose only that approved set to agents, generate a project-local mcpx

skill:

```bash

mcpx @skill --servers posthog,sentry

```

This writes:

```text

.agents/skills/mcpx/SKILL.md

```

For temporary agent guidance without writing `.agents/skills`, print a

single-server skill to stdout:

```bash

mcpx @skill --show slack

```

Use this when the user asks for a one-off service action during the current

agent session and does not want persistent project skills.

## References

mcpx maintains a background daemon (`mcpxd`) for session reuse and notification

buffering. You normally do not need to interact with it. If a tool call behaves

unexpectedly (stuck session, surprising eviction, schema drift), see

[references/daemon.md](references/daemon.md) before filing an issue.

## Feedback

If mcpx behaves unexpectedly, capture the exact command, schema selector, input,

and structured error, then file an issue:

```bash

gh issue create -R celados/mcpx --title "bug: <summary>" --body "<repro steps and error output>"

```