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Utter is the supply side of the agent economy: a sentence becomes a paid API. Distribution is how those APIs reach the agents that pay for them. The @utter/plugin-gen package turns your published endpoints into an installable Claude Code plugin marketplace, so any agent can add your marketplace and install an endpoint in one command. Each endpoint becomes a plugin whose bundled buyer MCP lets an agent discover, pay for, and call it through the escrow response gate. See the agent-facing side in Install as a Claude Code plugin.

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What it generates

1

Read the endpoints

It reads the public marketplace index (GET /resources), or a single agent card, or a file, and projects each endpoint to the fields a plugin needs (resource id, slug, price, reputation).
2

Build the plugins

A base utter-buyer plugin (discovery plus pay for any endpoint) and one utter-<slug> plugin per endpoint, each with a plugin.json, a skill, and a scoped buyer MCP server.
3

Write the marketplace

A .claude-plugin/marketplace.json that lists every plugin, plus the plugin folders under plugins/. Point Claude Code at the folder and the plugins install.

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Generate

The utter-plugins CLI writes the marketplace to disk.
Key flags:

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Two ways to launch the buyer MCP

The generated plugin.json declares one stdio MCP server. How it launches is a generation choice:
  • Local (--local): runs ${CLAUDE_PROJECT_DIR}/scripts/utter-buyer-mcp.mjs, so it works immediately for anyone running Claude Code inside the utter repo. No publish step. This is the Windows-safe launcher (an absolute path is valid as the main script argument, unlike node --import).
  • Published (--published): runs npx -y @utter/buyer-sdk utter-buyer-mcp, the standard form for a marketplace consumed outside the repo. It requires publishing @utter/buyer-sdk to a registry your users can reach.

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Publish the marketplace

Writing to the repo root makes the repository itself an installable marketplace:
Regenerate after each new endpoint is published (or on a schedule) to keep the marketplace in sync with the live index. Because the money fields are never authored by the generator, a stale or wrong row cannot cause a bad payment: the buyer SDK re-pins escrow, asset, payTo, and cap against the trusted on-chain constants on the served card before signing.

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Scope and safety

  • The generator is pure text and config. It never holds a key and never writes a secret into a committed file. Live plugins read the buyer key from the plugin’s sensitive user config at launch.
  • A per-endpoint plugin’s buyer MCP is scoped to one resource id (UTTER_RESOURCE_IDS), so it exposes only that endpoint’s call tool.
  • The base plugin runs in demo mode by default so it boots and demonstrates the full escrow loop with no configuration. Live endpoints activate when the live buyer path is provisioned. See Provisioning.