openmarketplace

A TypeScript library and CLI for converting AI coding agent plugins between formats. Parse a plugin from any supported agent, convert it to any other, and browse/install plugins from marketplace catalogs.

Why

Every AI coding agent has its own plugin format: Claude Code uses JSON manifests + SKILL.md, Codex uses TOML, Gemini CLI uses extension manifests, Cursor/Windsurf/Cline use their own MCP JSON layouts. A plugin written for one agent doesn't work in another.

openmarketplace solves this with an Intermediate Representation (IR). Each agent gets one adapter that can parse and emit. N adapters give N x N conversions without writing N x N individual converters.

Source Adapter (parse) --> Plugin IR --> Target Adapter (emit)

When a target agent doesn't support something (e.g., Cursor can't represent hooks), the converter drops it gracefully and returns a structured diagnostic explaining what was lost.

Supported agents

| Agent | MCP | Skills | Agents | Hooks | Context | Commands | LSP | |-------|:---:|:------:|:------:|:-----:|:-------:|:--------:|:---:| | Claude Code | stdio, http, sse | yes | yes | yes | yes | yes | yes | | Codex | stdio, http | yes | yes | - | yes | - | - | | Gemini CLI | stdio, http, sse | yes | yes | yes | yes | yes | - | | Cursor | stdio, http | - | - | - | - | - | - | | Windsurf | stdio, http, sse | - | - | - | - | - | - | | Cline | stdio, sse | - | - | - | - | - | - | | Continue | stdio, http, sse | - | - | - | - | - | - | | Amazon Q | stdio, http | - | - | - | - | - | - | | VS Code | stdio, http | - | - | - | - | - | - |

Install

npm install openmarketplace

Library usage

import { convert, parsePlugin, emitPlugin } from "openmarketplace";

// Convert a Claude Code plugin to Cursor format
const result = await convert({
  from: "claude-code",
  to: "cursor",
  files: {
    ".mcp.json": '{"mcpServers":{"fs":{"command":"npx","args":["-y","@anthropic/mcp-fs"]}}}',
    "skills/deploy/SKILL.md": "---\nname: deploy\ndescription: Deploy to prod\n---\nRun the deploy script.",
  },
});

console.log(result.files);
// { ".cursor/mcp.json": '{"mcpServers":{"fs":{"command":"npx","args":["-y","@anthropic/mcp-fs"]}}}' }

console.log(result.diagnostics);
// [{ level: "warning", message: "Target agent 'Cursor' does not support skills. 1 item(s) dropped.", field: "skills" }]

Two-step conversion

Parse once, emit to multiple targets:

const { plugin } = await parsePlugin("claude-code", { files });

const cursor  = await emitPlugin("cursor", plugin);
const codex   = await emitPlugin("codex", plugin);
const gemini  = await emitPlugin("gemini-cli", plugin);

Adapter discovery

import { listAdapters, getAdapter } from "openmarketplace";

listAdapters().forEach(a => {
  console.log(a.agent, a.displayName, a.capabilities());
});

const adapter = getAdapter("claude-code");
const { plugin } = await adapter.parse({ files });

Marketplace browsing

import { detectProvider } from "openmarketplace";

const provider = detectProvider("anthropics/plugins");
const listing = await provider.fetchListing("anthropics/plugins", { search: "mcp" });
console.log(listing.plugins.map(p => p.name));

CLI usage

# Convert a plugin directory
openmarketplace convert ./my-plugin --from claude-code --to gemini-cli --out ./output

# Dry run (show what files would be written)
openmarketplace convert ./my-plugin --from claude-code --to cursor --dry-run

# Browse a marketplace
openmarketplace browse anthropics/plugins
openmarketplace browse anthropics/plugins --search "deploy"

# Install a plugin for specific agents
openmarketplace install my-plugin@owner/repo --agents claude-code,cursor
openmarketplace install my-plugin@owner/repo --agents codex --scope global

# List installed plugins
openmarketplace list
openmarketplace list --agent cursor --format json

Install behavior

Plugins are installed directly into each target agent's native config location:

• Project scope (default): files are written/merged into the project directory
• Global scope (--scope global): files go to ~/.<agent>/ (e.g., ~/.cursor/, ~/.claude/)

When merging into an existing project:

• MCP JSON configs are deep-merged (existing servers are preserved)
• Context files (CLAUDE.md, AGENTS.md, GEMINI.md) are appended with a --- separator
• Everything else is written directly

Installation state is tracked at ~/.openmarketplace/installed.json.

Marketplace sources

The CLI accepts various source formats:

| Format | Example | Behavior | |--------|---------|----------| | GitHub shorthand | owner/repo | Clones https://github.com/owner/repo | | Git URL | https://github.com/org/repo.git | Clones directly | | HTTP URL | https://example.com/manifest.json | Fetches as JSON | | Local directory | ./path/to/plugin | Reads from disk |

Three marketplace formats are supported:

• Claude: repos containing marketplace.json
• OpenAI: repos with SKILL.md files in skills/, .system/, .curated/ directories
• Gemini: repos containing gemini-extension.json

The correct provider is auto-detected based on source string scoring.

The IR

The Plugin IR is the superset of all agent capabilities:

interface Plugin {
  name: string;
  version?: string;
  description?: string;
  author?: { name: string; email?: string; url?: string };
  license?: string;
  homepage?: string;
  repository?: string;
  keywords?: string[];
  mcpServers?: McpServer[];    // MCP server configs (stdio/http/sse)
  skills?: Skill[];             // SKILL.md instruction sets
  agents?: Agent[];             // Subagent definitions
  hooks?: Hook[];               // Lifecycle hooks (13 event types)
  contextFiles?: ContextFile[]; // CLAUDE.md / AGENTS.md / GEMINI.md
  commands?: Command[];         // Custom slash commands
  lspServers?: LspServer[];     // Language server configs
  extensions?: Record<string, unknown>;
}

Each field is optional. When converting to a target that doesn't support a field, it's dropped with a warning diagnostic.

Development

git clone https://github.com/alexngai/openmarketplace.git
cd openmarketplace
npm install
npm run build
npm test

| Script | Description | |--------|-------------| | npm run build | Compile TypeScript | | npm run typecheck | Type check without emitting | | npm test | Run 220 tests | | npm run test:watch | Watch mode | | npm run test:coverage | Coverage report |

License

MIT