Is the 21st MCP server down?

mcp-registry/dev.21st/mcp · v0.1.0

As of 2026-10-21 20:01 UTC, the 21st MCP server is up (it requires sign-in) with a Glimind reliability score of 83/100 (grade B). Over the last 30 days it answered 100% of Glimind's liveness checks.

Find UI components and themes, retrieve code, and generate with hosted 21st AI when enabled.

claude mcp add --transport http 21st-mcp-server https://21st.dev/api/mcp

{
  "mcpServers": {
    "21st-mcp-server": {
      "type": "http",
      "url": "https://21st.dev/api/mcp"
    }
  }
}

Third-party server, listed as discovered. Review its source before installing.

Agent-readiness: C (79/100)

What to fix (5)

Auto-fix: 17 corrected tool definitions

Paste-ready definitions with the problems above fixed. Changes marked verify need a human look. 1 tool(s) still need parameter descriptions written by someone who knows the API. All of them as JSON: /v1/readiness/mcp-registry%2Fdev.21st%2Fmcp/fixes

{
  "name": "add_to_list",
  "description": "Add (or with remove:true, remove) a component/theme/template to one of the caller's bookmark lists. Idempotent; adding also ensures the item is bookmarked. Use the list id from list_bookmark_lists and the item id+type from a search result.",
  "inputSchema": {
    "type": "object",
    "required": [
      "listId",
      "type",
      "id"
    ],
    "properties": {
      "id": {
        "type": [
          "number",
          "string"
        ],
        "description": "The item id (component demo id / theme uuid / template id)."
      },
      "type": {
        "enum": [
          "component",
          "theme",
          "template"
        ],
        "type": "string",
        "description": "What kind of item the id refers to."
      },
      "listId": {
        "type": "string",
        "description": "The bookmark list id (uuid)."
      },
      "remove": {
        "type": "boolean",
        "description": "Set true to remove the item from the list."
      }
    }
  },
  "annotations": {
    "readOnlyHint": false,
    "destructiveHint": true,
    "idempotentHint": true
  },
  "title": "Add / remove an item in a bookmark list"
}

{
  "name": "bookmark",
  "description": "Add (or with remove:true, delete) a bookmark - the 'heart'/save - for a component, theme, or template on the signed-in account. Idempotent. Use the id + type from a search or list result.",
  "inputSchema": {
    "type": "object",
    "required": [
      "type",
      "id"
    ],
    "properties": {
      "id": {
        "type": [
          "number",
          "string"
        ],
        "description": "The item id (component demo id / theme uuid / template id)."
      },
      "type": {
        "enum": [
          "component",
          "theme",
          "template"
        ],
        "type": "string",
        "description": "What kind of item the id refers to."
      },
      "remove": {
        "type": "boolean",
        "description": "Set true to remove the bookmark instead of adding it."
      }
    }
  },
  "annotations": {
    "readOnlyHint": false,
    "destructiveHint": false,
    "idempotentHint": false
  },
  "title": "Bookmark / unbookmark a 21st item"
}

{
  "name": "create_bookmark_list",
  "description": "Create a new personal named bookmark list on the signed-in account.",
  "inputSchema": {
    "type": "object",
    "required": [
      "name"
    ],
    "properties": {
      "name": {
        "type": "string",
        "description": "The list name."
      }
    }
  },
  "annotations": {
    "readOnlyHint": false,
    "destructiveHint": false,
    "idempotentHint": false
  },
  "title": "Create a bookmark list"
}

Get alerted

Get an email or webhook when this server's readiness drops by 10+ points, tool-poisoning text appears, or a tool breaks:

curl -X POST https://glimind.com/v1/subscriptions -H 'content-type: application/json' -d '{"tools":["mcp-registry/dev.21st/mcp"],"email":"[email protected]"}'

Agents: watch_tool({"toolId": "mcp-registry/dev.21st/mcp"}) over MCP.

Passed

• Every tool has a well-formed, typed input schema.
• No tool-poisoning patterns (hidden characters, instruction overrides, concealment, secret access, tool shadowing).
• Compact tool list (~3,398 tokens).
• Tool names are unique and portable across clients.
• 100.00% uptime over 30 days.
• No breaking contract changes in 30 days.

Largest tool definitions

• search ~476 tokens
• edit_template ~295 tokens
• edit_component ~211 tokens
• generate ~209 tokens
• add_to_list ~207 tokens

Static checks of the advertised tools/list (schema, descriptions, annotations, tool-poisoning patterns, names, size) plus observed protocol, uptime, latency and contract changes. Read-only: no tool is ever called. Weights: schema 15, docs 20, safety 15, efficiency 15, compatibility 15, protocol 5, reliability 10, stability 5. Token counts are estimates (~3.6 characters per token).

Operator? Fix these, then re-check live. Embed the readiness badge:

[![MCP agent-readiness](https://glimind.com/v1/readiness/badge/mcp-registry%2Fdev.21st%2Fmcp.svg)](https://glimind.com/server/mcp-registry%2Fdev.21st%2Fmcp?ref=badge)

<a href="https://glimind.com/server/mcp-registry%2Fdev.21st%2Fmcp?ref=badge"><img src="https://glimind.com/v1/readiness/badge/mcp-registry%2Fdev.21st%2Fmcp.svg" alt="MCP agent-readiness"></a>

.. image:: https://glimind.com/v1/readiness/badge/mcp-registry%2Fdev.21st%2Fmcp.svg
   :target: https://glimind.com/server/mcp-registry%2Fdev.21st%2Fmcp?ref=badge
   :alt: MCP agent-readiness

Tool-definition log

Glimind records every version of this server's tool definitions in a signed, append-only transparency log. Current manifest sha256:ab592c78a684df8d…, first seen 2026-10-17, included at leaf 3353 of 41,379. Version history · verify what your client received.

Tools (21)

• add_to_list
• bookmark
• create_bookmark_list
• delete_component
• delete_template
• delete_theme
• edit_component
• edit_template
• edit_theme
• generate
• get_bookmark_list
• get_component
• get_theme
• get_usage
• list_bookmark_lists
• list_bookmarks
• list_team_components
• list_team_libraries
• list_team_lists
• list_teams
• search

Compare: most reliable productivity servers · most reliable other servers · most reliable code servers · most reliable web servers · most reliable data servers

claude mcp add --transport http glimind https://glimind.com/mcp

{
  "mcpServers": {
    "glimind": {
      "type": "http",
      "url": "https://glimind.com/mcp"
    }
  }
}

FAQ

Is the 21st MCP server down right now?

As of 2026-10-21 20:01 UTC, the 21st MCP server is up (it requires sign-in) with a Glimind reliability score of 83/100 (grade B). Over the last 30 days it answered 100% of Glimind's liveness checks.

How many tools does 21st MCP server provide?

21st MCP server advertises 21 tools, including add_to_list, bookmark, create_bookmark_list, delete_component, delete_template.

How do I install 21st MCP server?

Point your MCP client at this streamable-http endpoint: https://21st.dev/api/mcp

Is the 21st MCP server safe to connect to an AI agent?

Glimind scanned all 21 tool definitions for tool-poisoning patterns — hidden or invisible characters, instructions that override the model, concealment from the user, requests to read credential or MCP config files, conversation exfiltration and cross-tool shadowing — and found none. This checks what the server tells the model, not what its code does; review the source before granting access to sensitive data.

Operator of 21st MCP server?

Status page: 90-day uptime, every outage and how long it lasted.

Claim this listing to get the Verified operator marker, a remediation checklist and owner analytics, or embed the live badge from any of the tool pages above. Maintainers: alerts, deploy attestation and monthly reports.

Status is an automated estimate from Glimind's liveness checks (handshake and tool listing only; no tool is ever called) and may lag or differ from your network. Glimind is not affiliated with this server or its operator. Operator? Request a correction or opt out at https://glimind.com/opt-out.