Cosmic MCP Server
An MCP (Model Context Protocol) server that exposes Cosmic CMS functionality as tools for AI assistants. Manage your content, media, object types, and generate AI content directly through Claude, Cursor, or any MCP-compatible client.
Features
- Content Management: Create, read, update, and delete objects in your Cosmic bucket
- Media Management: Upload, list, and manage media files
- Schema Management: Create and modify object types with custom metafields
- AI Generation: Generate text, images, and videos using Cosmic's AI capabilities
Hosted endpoint (recommended)
Cosmic operates a hosted streamable-HTTP MCP server. No install required.
URL: https://mcp.cosmicjs.com/v1/buckets/{bucket-slug}
Cosmic uses separate read and write keys per bucket. Authenticate with one of:
Authorization: Bearer <read_key> # read-only tools
Authorization: Bearer <read_key>:<write_key> # full access
You can also send the write key out-of-band via the X-Cosmic-Write-Key header if your client can't colon-pack the bearer token. Keys are issued in your bucket's API Access settings in the Cosmic dashboard.
Use the read key for read-only access (list/get tools), or the write key for full access including object creation, media upload, and AI generation.
Claude Desktop (remote MCP)
In Claude Desktop, Settings -> Connectors -> Add custom connector, enter:
- URL:
https://mcp.cosmicjs.com/v1/buckets/your-bucket-slug
- Bearer token:
<read_key> for read-only access, or <read_key>:<write_key> for full access
Cursor (remote MCP)
Add to .cursor/mcp.json:
{
"mcpServers": {
"cosmic": {
"url": "https://mcp.cosmicjs.com/v1/buckets/your-bucket-slug",
"headers": {
"Authorization": "Bearer your-bucket-read-key:your-bucket-write-key"
}
}
}
}
Local installation (stdio)
For environments without remote MCP support, the same server runs locally over stdio.
Using npx (recommended)
Global installation
npm install -g @cosmicjs/mcp
cosmic-mcp
From source
git clone https://github.com/cosmicjs/mcp.git
cd mcp
bun install
bun run build
Configuration
The server requires the following environment variables:
| Variable | Required | Description |
|---|
COSMIC_BUCKET_SLUG | Yes | Your Cosmic bucket slug |
COSMIC_READ_KEY | Yes | Bucket read key for read operations |
COSMIC_WRITE_KEY | No | Bucket write key for write operations |
Getting your credentials
- Log in to your Cosmic dashboard
- Navigate to your bucket
- Go to Settings → API Access
- Copy your bucket slug, read key, and write key
Local stdio with Claude Desktop
If you prefer to run the MCP server locally rather than use the hosted endpoint, add the following to your Claude Desktop configuration file.
macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
{
"mcpServers": {
"cosmic": {
"command": "npx",
"args": ["@cosmicjs/mcp"],
"env": {
"COSMIC_BUCKET_SLUG": "your-bucket-slug",
"COSMIC_READ_KEY": "your-read-key",
"COSMIC_WRITE_KEY": "your-write-key"
}
}
}
}
Local stdio with Cursor
{
"mcpServers": {
"cosmic": {
"command": "npx",
"args": ["@cosmicjs/mcp"],
"env": {
"COSMIC_BUCKET_SLUG": "your-bucket-slug",
"COSMIC_READ_KEY": "your-read-key",
"COSMIC_WRITE_KEY": "your-write-key"
}
}
}
}
Objects
| Tool | Description |
|---|
cosmic_objects_list | List objects with optional type filter, status, and pagination |
cosmic_objects_get | Get a single object by ID or slug |
cosmic_objects_create | Create a new object (requires write key) |
cosmic_objects_update | Update an existing object (requires write key) |
cosmic_objects_delete | Delete an object (requires write key) |
| Tool | Description |
|---|
cosmic_media_list | List media files with optional folder filter |
cosmic_media_get | Get media details by ID |
cosmic_media_upload | Upload media from URL or base64 (requires write key) |
cosmic_media_delete | Delete a media file (requires write key) |
Object Types
| Tool | Description |
|---|
cosmic_types_list | List all object types in the bucket |
cosmic_types_get | Get object type schema by slug |
cosmic_types_create | Create a new object type (requires write key) |
cosmic_types_update | Update object type schema (requires write key) |
cosmic_types_delete | Delete an object type (requires write key) |
AI Generation
| Tool | Description |
|---|
cosmic_ai_generate_text | Generate text content using AI |
cosmic_ai_generate_image | Generate and upload an AI image (requires write key) |
cosmic_ai_generate_video | Generate and upload an AI video (requires write key) |
Content Blocks
| Tool | Description |
|---|
cosmic_blocks_list | List the bucket's reusable rich-text Content Blocks (the {{name /}} tokens available in rich-text fields) |
Example Prompts
Here are some example prompts you can use with Claude or Cursor:
Content Management
List all blog posts in my Cosmic bucket
Create a new blog post titled "Getting Started with MCP" with the content "This is an introduction to the Model Context Protocol..."
Update the blog post with ID "abc123" to change its status to published
Show me all images in the "blog-images" folder
Upload this image URL to my media library: https://example.com/image.jpg
Schema Management
Show me all object types in my bucket
Create a new object type called "Products" with fields for name, price, description, and image
AI Generation
Generate a product description for a wireless bluetooth headphone
Generate an image of a futuristic city skyline at sunset and upload it to my media library
Development
Build
This produces two binaries:
dist/stdio.js - npm-published stdio entry (bin: cosmic-mcp)dist/http.js - hosted streamable-HTTP entry (deployed to ECS Fargate)
Watch mode (stdio)
Run locally (stdio)
COSMIC_BUCKET_SLUG=your-bucket \
COSMIC_READ_KEY=your-read-key \
COSMIC_WRITE_KEY=your-write-key \
bun run start
Run locally (HTTP)
Deployment
Pushes to main deploy to https://mcp.cosmicjs.com via GitHub Actions. Workflow: .github/workflows/deploy.yml.
Releasing to npm
Releases are driven by Changesets. Every change that should ship adds a changeset (bunx changeset) describing the bump (patch | minor | major).
To cut a release, run one command from a clean main:
This consumes the pending changesets to bump the version, refreshes the lockfile, commits chore(release): vX.Y.Z, then tags and pushes. It prompts once before the tag push (pass -- --yes to skip). Pushing the tag triggers the publish.yml workflow, which verifies the tag matches package.json, builds, and runs npm publish --provenance --access public (requires the NPM_TOKEN repo secret).
Do not hand-edit the version field in package.json; let the changeset bump it. The release also runs scripts/sync-version.mjs, which copies the new version into server.json and SERVER_VERSION in src/server.ts so all three always agree. If you ever need to publish directly from your machine (with a local npm token, no provenance), bun run release:direct runs changeset publish.
Publishing to the MCP registry
The server is listed on registry.modelcontextprotocol.io under the com.cosmicjs namespace, described by server.json.
Order matters: the registry verifies the listing against what is actually on npm, so release to npm first and publish the listing second. mcpName in package.json must always equal name in server.json, which is how the registry proves we own the npm package.
One-time setup to prove domain ownership. This uses ECDSA P-384 because macOS ships LibreSSL, which cannot generate Ed25519 keys (brew install openssl@3 if you prefer Ed25519):
openssl genpkey -algorithm EC -pkeyopt ec_paramgen_curve:secp384r1 -out key.pem
PUBLIC_KEY="$(openssl ec -in key.pem -text -noout -conv_form compressed | grep -A4 "pub:" | tail -n +2 | tr -d ' :\n' | xxd -r -p | base64)"
echo "cosmicjs.com. IN TXT \"v=MCPv1; k=ecdsap384; p=${PUBLIC_KEY}\""
Add that TXT record on the apex of cosmicjs.com. A selector such as _mcp-auth.cosmicjs.com will not be found and fails with a generic signature error. The apex TXT set also holds the SPF and Google verification records, so append to it rather than replacing it. Keep key.pem out of the repo; it lives in ~/.cosmic-mcp/key.pem.
Then, after each npm release, publish the listing (brew install mcp-publisher first):
PRIVATE_KEY="$(openssl ec -in ~/.cosmic-mcp/key.pem -noout -text | grep -A4 "priv:" | tail -n +2 | tr -d ' :\n')"
mcp-publisher login dns --algorithm ecdsap384 --domain cosmicjs.com --private-key "${PRIVATE_KEY}"
mcp-publisher publish
--algorithm ecdsap384 is required. The publisher defaults to ed25519 and rejects the P-384 key with invalid seed length: expected 32 bytes, got 48, which reads like a corrupt key rather than a wrong algorithm.
API Reference
For more information about the Cosmic API, see:
License
MIT
Contributing
Contributions are welcome! Please open an issue or submit a pull request.
Support