docs: say what the toolkit is, and that an account is required

Two gaps a cold reader walked into. The README never mentioned the MCP
server or how the three pieces relate, so the CLI read as the entire
product. And it said nothing about needing a Reply.io account: someone
without one had no way to learn that `reply auth login` can create one,
or that execution always runs against Reply.io rather than a local mode.

Add the shared three-surface block, worded identically in all three
repositories, and open Authentication with what the account buys and what
this project is not.

Author: ArtemKosolap

README.md

@@ -55,6 +55,22 @@ after a second and a half, and stays silent when it fails. It never runs for any
 other command, and never at all with `--json`, when output is piped, in CI, or
 with `REPLY_NO_UPDATE_CHECK=1` set.
 
+## Where this fits
+
+Reply's agentic toolkit is three pieces. They are complementary, not alternatives:
+
+| | What it is | When you want it |
+|---|---|---|
+| **reply CLI** (this repo) | `npm i -g reply-cli` — authenticated access to *every* v3 endpoint via `reply api` | Your agent has a shell. This is the complete surface. |
+| **[Reply MCP](https://github.com/reply-team/reply-mcp)** | A curated tool catalog over `mcp.reply.io` | Your client speaks MCP and has no shell — desktop apps, hosted assistants. |
+| **[reply-skills](https://github.com/reply-team/reply-skills)** | Outbound expertise as markdown skills: what to do, in what order, with what guardrails | Your agent knows *how* to call things but not *what* to run. |
+
+MCP gives your agent tools. Skills give it judgement. Most setups want both; a shell-capable
+agent can do everything through the CLI alone.
+
+The shortest path that works: install the CLI, `reply auth login`, `reply skills install`, then
+talk to your agent in plain words. MCP is optional — add it when your client has no shell.
+
 ## Usage
 
 ```sh
@@ -67,6 +83,16 @@ machine-readable output suitable for scripts.
 
 ## Authentication
 
+**You need a Reply.io account.** If you have one, sign in with it. If you don't, `reply auth
+login` takes you to the browser, where you can create one and start a free trial — no credit
+card. The CLI, the skill packs and the local tooling are free and open source; what a Reply.io
+account gives you is the execution: mailboxes, sending, the contact store, the inbox, analytics.
+
+> **Open source, not self-hosted.** The CLI and the skill packs are MIT and yours to fork.
+> Execution always runs against Reply.io — the API, the hosted MCP server at `mcp.reply.io`,
+> your mailboxes and your data. There is no local mode, and outreach without a Reply.io account
+> is not something this toolkit can do.
+
 Log in through your browser with OAuth:
 
 ```sh