JSR MCP: Give Your LLM Complete Access to the JavaScript Registry

I just published an MCP server that gives Claude, GPT-4, or any MCP-compatible LLM full access to JSR - the JavaScript Registry. Here's how to search packages, manage scopes, and even publish new versions, all through natural language.

What This Package Does

The @wyattjoh/jsr-mcp package is a Model Context Protocol server that exposes the entire JSR API to LLMs. It implements all 50+ endpoints from the JSR API specification, from simple package searches to complex authorization flows.

Now available on JSR: jsr.io/@wyattjoh/jsr-mcp

Getting Started with Claude Desktop

Let me walk you through the setup. First, make sure you have Claude Desktop (version 0.7.0 or later).

Edit your Claude Desktop configuration:

1# On macOS
2code ~/Library/Application\ Support/Claude/claude_desktop_config.json

Add the JSR server to your MCP servers:

1{
2  "mcpServers": {
3    "jsr": {
4      "command": "deno",
5      "args": [
6        "run",
7        "--allow-env=JSR_API_URL,JSR_REGISTRY_URL,JSR_API_TOKEN",
8        "--allow-net=api.jsr.io,jsr.io",
9        "jsr:@wyattjoh/jsr-mcp"
10      ]
11    }
12  }
13}

Restart Claude Desktop. The MCP connection indicator will show it's active.

What You Can Actually Do

Once connected, you can ask Claude things like:

"Search for testing packages on JSR"

Claude will call the search tool and return results:

1await jsr_search_packages({
2  query: "testing",
3  limit: 10
4});
5// Returns packages like @std/testing, @mock/test, etc.

"Show me all versions of @oak/oak"

1await jsr_list_package_versions({
2  scope: "oak",
3  name: "oak"
4});
5// Returns all published versions with metadata

"What's the quality score of @std/fs?"

1await jsr_get_package_score({
2  scope: "std",
3  name: "fs"
4});
5// Returns documentation, compatibility, and quality metrics

Public vs Authenticated Operations

The server works in two modes:

Public Mode (No Token Required)

Most read operations work without authentication:

1{
2  "mcpServers": {
3    "jsr": {
4      "command": "deno",
5      "args": [
6        "run",
7        "--allow-env=JSR_API_URL,JSR_REGISTRY_URL,JSR_API_TOKEN",
8        "--allow-net=api.jsr.io,jsr.io",
9        "jsr:@wyattjoh/jsr-mcp"
10      ]
11    }
12  }
13}

This gives you:

Package search and discovery
Version information
Dependency analysis
User and scope lookups
Registry statistics

Authenticated Mode (With API Token)

For package management, you need a JSR API token:

1{
2  "mcpServers": {
3    "jsr": {
4      "command": "deno",
5      "args": [
6        "run",
7        "--allow-env=JSR_API_URL,JSR_REGISTRY_URL,JSR_API_TOKEN",
8        "--allow-net=api.jsr.io,jsr.io",
9        "jsr:@wyattjoh/jsr-mcp"
10      ],
11      "env": {
12        "JSR_API_TOKEN": "your-jsr-api-token"
13      }
14    }
15  }
16}

Get your token at jsr.io/account/tokens.

This unlocks:

Creating and managing scopes
Publishing packages and versions
Managing scope members
Updating package metadata
Yanking versions

The Complete Tool Arsenal

The server exposes 50+ tools covering every JSR operation. Here are the categories:

Package Discovery & Information

jsr_search_packages - Full-text package search
jsr_get_package - Detailed package information
jsr_get_package_metadata - Registry metadata
jsr_get_package_score - Quality metrics
jsr_list_packages - Browse all packages

Version Management

jsr_list_package_versions - All versions of a package
jsr_get_package_version - Specific version details
jsr_create_package_version - Publish new versions
jsr_update_package_version - Yank versions

Dependency Analysis

jsr_get_package_dependencies - What a package depends on
jsr_get_package_dependents - What depends on a package

Scope Operations

jsr_create_scope - Create new scopes
jsr_update_scope - Configure scope settings
jsr_list_scope_packages - Packages in a scope
jsr_list_scope_members - Scope collaborators

User Management

jsr_get_current_user - Your JSR profile
jsr_get_user_scopes - User's scope memberships
jsr_accept_scope_invite - Join scopes
jsr_add_scope_member - Invite collaborators

Real-World Examples

Here's what people are using this for:

Package Discovery

"Find all Deno-compatible HTTP servers"
"What testing frameworks support both Node and Deno?"
"Show me packages by the Deno team"

Dependency Research

"What packages depend on @std/fs?"
"Show me the dependency tree for @oak/oak version 12.0.0"
"Find packages with zero dependencies"

Quality Analysis

"Compare quality scores of all markdown parsers"
"Which @std packages have the best documentation?"
"Find packages with 100% browser compatibility"

Package Management (with token)

"Create a new scope for my company"
"Publish version 2.0.0 of my package"
"Add john@example.com as admin to @mycompany scope"
"Yank the broken 1.2.3 version"

Publishing Packages Through Claude

With authentication, Claude can publish packages for you:

1// Claude can execute this flow:
2await jsr_create_scope({
3  scope: "mycompany",
4  description: "Corporate packages"
5});
6
7await jsr_create_package({
8  scope: "mycompany",
9  package: "utils"
10});
11
12await jsr_create_package_version({
13  scope: "mycompany",
14  name: "utils",
15  version: "1.0.0",
16  configPath: "deno.json",
17  tarballPath: "./dist/package.tar.gz"
18});

You prepare the tarball, Claude handles the JSR API calls.

Advanced: Authorization Flows

The server even supports OAuth-style authorization flows:

1// Start authorization
2const auth = await jsr_create_authorization({
3  challenge: "random-string",
4  permissions: [{ scope: "package:write" }]
5});
6
7// User approves in browser
8await jsr_approve_authorization({
9  code: auth.code
10});
11
12// Exchange for token
13const token = await jsr_exchange_authorization({
14  exchangeToken: auth.exchangeToken,
15  verifier: "challenge-verifier"
16});

This enables building custom JSR integrations through Claude.

Local Development

Clone and run locally:

1git clone https://github.com/wyattjoh/jsr-mcp
2cd jsr-mcp/packages/jsr-mcp
3
4# Or build a binary
5deno task build
6./jsr-mcp

Configuration Options

Three environment variables control the server:

JSR_API_TOKEN - Your authentication token
JSR_API_URL - Custom API endpoint (default: https://api.jsr.io)
JSR_REGISTRY_URL - Custom registry URL (default: https://jsr.io)

What's Next

Some ideas for future enhancements:

Bulk operations for managing multiple packages
Package migration tools from npm
Automated compatibility testing
Package analytics and insights
CI/CD integration helpers

Try It Now

Install Claude Desktop or Claude Code
Add the configuration above
Start exploring JSR through natural language

Or use it programmatically:

1deno add @wyattjoh/jsr-mcp

The full source is at github.com/wyattjoh/jsr-mcp.

Have questions or feature requests? Open an issue on GitHub or reach out on BlueSky @wyattjoh.

1{ 2 "mcpServers": { 3 "jsr": { 4 "command": "deno", 5 "args": [ 6 "run", 7 "--allow-env=JSR_API_URL,JSR_REGISTRY_URL,JSR_API_TOKEN", 8 "--allow-net=api.jsr.io,jsr.io", 9 "jsr:@wyattjoh/jsr-mcp" 10 ] 11 } 12 } 13}

1// Claude can execute this flow: 2await jsr_create_scope({ 3 scope: "mycompany", 4 description: "Corporate packages" 5}); 6 7await jsr_create_package({ 8 scope: "mycompany", 9 package: "utils" 10}); 11 12await jsr_create_package_version({ 13 scope: "mycompany", 14 name: "utils", 15 version: "1.0.0", 16 configPath: "deno.json", 17 tarballPath: "./dist/package.tar.gz" 18});

1// Start authorization 2const auth = await jsr_create_authorization({ 3 challenge: "random-string", 4 permissions: [{ scope: "package:write" }] 5}); 6 7// User approves in browser 8await jsr_approve_authorization({ 9 code: auth.code 10}); 11 12// Exchange for token 13const token = await jsr_exchange_authorization({ 14 exchangeToken: auth.exchangeToken, 15 verifier: "challenge-verifier" 16});