AgentParley

Building

Quickstart — your first plugin

Write a plugin, publish it, install it, and watch it change an agent's reply.

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In about ten minutes you will build a plugin that makes every agent on your account end its replies with a sign-off you choose, publish it privately, install it, and see it work in a chat.

It is the same shape as the official Caveman and My Dude plugins: one systemPrompt middleware that adds a line to the agent's instructions before each turn.

You need an AgentParley account with a model provider connected and one agent that replies.

1. Create the plugin

Skip this step if you take option B below: uploading a zip creates the plugin from its readme.

In the console, open Plugins → Created → Write in the browser. Fill in:

  • Name — Sign-off
  • Address — sign-off (lowercase letters, digits, hyphens and underscores, up to 64 characters; it becomes part of your plugin's identity and of any tool names it registers)
  • One line about it — Ends every reply with a sign-off.
  • Start from — any card; you will replace the code.

Press Create and open editor.

2. Write the code

You can write it in the console editor (option A) or on your machine and upload a zip (option B). The code is the same.

globalThis.manifest = {
  settings: [
    {
      key: "signOff",
      title: "Sign-off",
      description: "The words every reply ends with.",
      type: "text",
      default: "Fair winds.",
    },
  ],
};

globalThis.middleware.systemPrompt = async (context) => {
  const signOff = host.settings.get("signOff");
  host.log("debug", `adding sign-off for agent ${context.agentId}`);
  return (
    context.systemPrompt +
    "\n\n## Sign-off\n" +
    `End every reply with the words "${signOff}", as the last words of your final sentence.`
  );
};

What each part does:

  • globalThis.manifest.settings declares a settings form. The user sees a Sign-off text field when they configure the plugin; your code reads it with host.settings.get("signOff").
  • globalThis.middleware.systemPrompt is a middleware hook. It runs every time an agent on the installing account starts a turn, receives the system prompt that turn is about to use, and returns the new one.
  • host.log writes a line to the plugin's log panel. It needs no permission.

The code calls no host.fetch, host.session or host.agents, so the plugin asks for no permissions.

Option A — the console editor

On the plugin's page, paste the code into the Code card (the editor's single file is index.js; TypeScript-only syntax such as type annotations won't work there — the code above is plain JavaScript and works in both). The card's Web addresses it can reach and Extra permissions fields are added to your manifest, and they win over the same keys in your code. Press Save (⌘S) to check that it builds.

Option B — a local folder and a zip

sign-off/
  readme.md
  index.ts
  tsconfig.json        (for your editor only — leave it out of the zip)

readme.md:

---
name: Sign-off
description: Ends every reply with a sign-off.
---

# Sign-off

Adds one line to every agent's instructions so each reply ends with the sign-off you set.

## Settings

- **Sign-off** — the words every reply ends with. Default: "Fair winds."

## Permissions

None.

index.ts is the code above. For type-checking, press Download SDK types on the plugin's page (it saves agentparley-plugin-sdk.d.ts) and use a tsconfig.json like this:

{
  "compilerOptions": {
    "strict": true,
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "lib": ["ES2022"],
    "types": [],
    "skipLibCheck": true,
    "noEmit": true
  },
  "include": ["index.ts", "agentparley-plugin-sdk.d.ts"]
}

Run npx tsc -p . to check it. The platform does not type-check at publish — it only strips the types — so this is your safety net. Then zip readme.md and index.ts (not tsconfig.json — the publish refuses files it doesn't recognize — and leave the .d.ts out too, since it would only count as an extra source file).

3. Publish

  • Editor: press Publish…. The first version becomes 1.0.0.
  • Zip: on Plugins → Created press Upload a plugin (or drop the zip there) and pick the zip. The readme has no version:, so the platform uses 1.0 and publishes 1.0.0.

Publishing bundles your code, discovers the capability (one systemPrompt middleware), derives the permissions (none), and stores version 1.0.0. Versions are immutable: the next change is 1.0.1 or higher.

Your plugin is private: only your account can see and install it. That is exactly what you want while testing.

4. Install and configure

Open Plugins → Browse. Your plugin is listed marked private. Open it — you'll see its capabilities, What it can reach (nothing), and your readme — and press Install Sign-off. Leave All agents selected and press Install on all agents.

On the installed plugin's page, set Sign-off to something you'll recognize, for example Ahoy, matey.

5. See it work

Open a new chat with any agent and ask it anything. The reply ends with Ahoy, matey.

There is nothing to enable per agent: middleware runs for every agent the plugin is installed on, and All agents is the default. (Tools, commands and skills are different — each agent's Access tab can narrow those.)

Back on the installed plugin's page, the logs panel shows your adding sign-off for agent … lines. Logs are kept for 24 hours.

6. Change it

Edit the text and publish the next version, and your install moves to it within about five minutes (the install's version policy is Latest by default). Zip: upload it again; the platform publishes 1.0.1. Editor: Publish… offers patch, minor and major for any published plugin. If a new version asks for more access — say you add host.fetch and an egress host — it waits on the installed plugin's page under Update waiting for your OK until you accept it.

To test changes before publishing, use Save in the editor and switch your install to your draft (Use my draft) on the Try it tab, where you can also chat with an agent running it.

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