> ## Documentation Index
> Fetch the complete documentation index at: https://docs.utter.technology/llms.txt
> Use this file to discover all available pages before exploring further.

# Install as a Claude Code plugin

> Install an Utter API as a Claude Code plugin and let your agent discover, pay for, and call it in one command.

Every Utter endpoint can be published as a Claude Code plugin. Installing one gives your agent
the buyer tools to discover Utter APIs, pay for them per call in USDC on Arc, and call them,
with the buyer key held only inside the local MCP process. Payment runs through the
[escrow response gate](/concepts/escrow-response-gate): you are charged only after the
response passes validation.

This is the same buyer flow as [the MCP server](/pay/mcp), packaged so a single
`/plugin install` wires it up.

## Two kinds of plugin

<CardGroup cols={2}>
  <Card title="utter-buyer (the base plugin)">
    Discovery plus pay tools for any Utter endpoint. Ships in demo mode: it boots with no
    configuration and runs the full discover, reserve, pay, and settle loop in-process against
    a mock chain, so you can see how paying for an API works with no real money.
  </Card>

  <Card title="utter-<slug> (one per endpoint)">
    A plugin scoped to a single published endpoint. It exposes just that endpoint's call tool
    and carries a skill describing what it does, its price, and its reputation. It runs in live
    mode against the real resource.
  </Card>
</CardGroup>

## Install

Add the marketplace once, then install a plugin from it.

```bash theme={null}
# From the utter repository (works today, no publish needed)
/plugin marketplace add ./          # or an absolute path to your utter checkout

# Or from GitHub once the repo is pushed
/plugin marketplace add <your-org>/utter
```

```bash theme={null}
# The base buyer plugin (demo mode, zero config)
/plugin install utter-buyer@utter

# A specific endpoint (live mode)
/plugin install utter-return-the-current-utc-time-as-json@utter
```

When the plugin is enabled, its bundled `utter-buyer` MCP server starts automatically. Claude
lists its tools as `mcp__plugin_<plugin-name>_utter-buyer__<tool>`.

## The tools

The bundled MCP server exposes the same two tools as [the MCP server](/pay/mcp):

<AccordionGroup>
  <Accordion title="utter_discover_endpoints">
    Lists or searches paid endpoints, projecting only price, reputation, and bond to the model.
    In a per-endpoint plugin, discovery is scoped to that one resource.
  </Accordion>

  <Accordion title="utter_call_[resourceId]">
    One tool per endpoint, named with the full 32-byte resource id. It validates your input
    before paying, reserves the per-call cap, pays through the escrow gate, and returns the
    response text. The buyer key is never a tool argument or return.
  </Accordion>
</AccordionGroup>

## Configure a live plugin

A live plugin (any per-endpoint plugin, or the base plugin switched to live) reads two values
from the plugin's configuration:

<ParamField path="buyer_private_key" type="string">
  A funded Arc testnet buyer key. Held only inside the local MCP process to sign USDC escrow
  payments. It never leaves your machine and is never a tool argument, a tool return, or a log
  line. Marked sensitive, so Claude Code stores it securely.
</ParamField>

<ParamField path="marketplace_url" type="string">
  The Utter marketplace base URL the buyer reads for discovery (it fetches `GET {url}/resources`).
</ParamField>

<Info>
  The base `utter-buyer` plugin works immediately in demo mode. A live plugin also needs the
  operator-gated live buyer path provisioned (the same gate as the rest of live Utter). See
  [Provisioning](/operator/provisioning).
</Info>

## Budgets and safety

Per-call and per-day budget caps bound what any tool will spend. A cap denial returns a tool
error with no charge. See [Deposits and spend caps](/pay/deposits-and-caps). The on-chain
signed cap is the hard per-call bound regardless.

## How these are made

Operators generate the whole marketplace from the live index with one command. See
[The plugin marketplace](/operator/plugin-marketplace).