Polar MCP Authentication Error in Claude Code

[victorcheeney]

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Description

Unable to authenticate with Polar MCP server in Claude Code. Following the official Polar MCP documentation for Claude Code setup results in authentication error.

Polar MCP Documentation: https://docs.polar.sh/integrate/mcp

Current Behavior

> /mcp
╭───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ Polar MCP Server                                                                                                                                                              │
│                                                                                                                                                                               │
│ Status: △ needs authentication                                                                                                                                                │
│ URL: https://mcp.polar.sh/mcp/polar-mcp                                                                                                                                       │
│ Config location: /Users/username/.claude.json [project: /Users/username/Development/project]                                                                      │
│                                                                                                                                                                               │
│ Error: The client cannot authenticate with methods: ['client_secret_basic', 'client_secret_post', 'none']                                                                     │
│                                                                                                                                                                               │
│ ❯ 1. Authenticate                                                                                                                                                             │
│   2. Disable                                                                                                                                                                  │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
   Esc to go back

Key Error:

Error: The client cannot authenticate with methods: ['client_secret_basic', 'client_secret_post', 'none']

Expected Behavior

MCP server should connect successfully and allow access to Polar organization without authentication errors.

Steps to Reproduce

1. Run the command from Polar documentation for Claude Code:

   claude mcp add --transport http "Polar" "https://mcp.polar.sh/mcp/polar-mcp"
   

2. Check MCP status with /mcp command in Claude Code

3. Authentication error appears with no clear way to provide credentials

Setup Used

Command (from Polar docs):

claude mcp add --transport http "Polar" "https://mcp.polar.sh/mcp/polar-mcp"

Config Location: /Users/username/.claude.json (user-level config)

Server URL: https://mcp.polar.sh/mcp/polar-mcp

Environment

• Operating System: macOS (Tahoe 26.0.1)
• Client: Claude Code (MCP-enabled)
• MCP Transport: HTTP (as specified in Polar docs)

Screenshots