Best Auth APIs for AI Agents, Independently Tested on 12 Coding Agents (2026)
Lightsage ·
Direct answer
Pick Clerk for startup and consumer login, WorkOS for B2B SSO and directory sync, and Supabase if your app already runs on Supabase Postgres. For an auth MCP server, pick Descope. All six tools below are agent-ready: each scored B or above when 12 coding agents did the same real task with them in Devtool Arena's October 2026 tests.
"Agent-ready" here means a company score of 75 (B) or higher on Devtool Arena (devtoolarena.com), Lightsage's public leaderboard of how well coding agents use real developer tools. Every auth tool got the same task, agents and grader. The rules are on the methodology page.
The 6 agent-ready auth APIs
Clerk, WorkOS and Supabase are within 1.2 points of each other.
1. Clerk: 84.6 (B)
Clerk is the auth API to start with for a consumer launch, and it scored B or above with all 12 agents.
- Best for: startup and consumer login
- Best agent result: 95 (A) on Cursor; first on 7 of 12 agents
- Agent assets: all 7 readiness assets, including a remote MCP server at
https://mcp.clerk.com/mcp - Free tier or price: the free Hobby plan covers 50,000 monthly retained users per app (pricing)
2. WorkOS: 84.1 (B)
Reach for WorkOS when your first enterprise customer asks for SAML. Its Python SDK keeps SSO, directory sync and invitations in separate namespaces.
- Best for: B2B SSO and directory sync
- Best agent result: 95 (A) on Cursor; first on 5 of 12 agents; #1 on both CLI boards (79)
- Agent assets: all 7 readiness assets, including a remote MCP server that manages SSO connections
- Free tier or price: AuthKit is free up to 1 million monthly active users, with no card until production (pricing)
3. Supabase: 83.4 (B)
Supabase Auth stores users in your project's Postgres and works with Row Level Security (docs).
- Best for: apps built on Supabase Postgres
- Best agent result: 93 (A) on Hermes and 90 (A) on Claude Code; first on 5 of 12 agents
- Agent assets: all 7 readiness assets, including a remote MCP server at
https://mcp.supabase.com/mcp - Free tier or price: SAML 2.0 SSO needs Pro or above (SSO guide)
4. Descope: 78.2 (B)
Descope's MCP server manages users, flows, audit logs and tenants, and its sessions start read-only.
- Best for: an auth MCP server, or SSO on a free plan
- Best agent result: 90 (A) on Hermes; #1 on Claude Code's MCP board (84)
- Agent assets: 6 of 7 readiness assets, including a remote MCP server at
https://mcp.descope.com(US) - Free tier or price: Free Forever includes 3 SSO connections; SCIM is on Growth, from $799 a month billed annually (pricing)
5. Scalekit: 77.8 (B)
Scalekit covers SSO and SCIM for B2B SaaS, and its AgentKit lists 600+ connectors. It sits 0.4 points behind Descope.
- Best for: SaaS products that also ship agents
- Best agent result: 82 (B) on OpenCode; tied first on Codex at 80
- Agent assets: all 7 readiness assets, including a hosted MCP server at
https://mcp.scalekit.com - Get started: the
scalekit-sdk-pythonpackage (SDK, pricing)
6. Auth0: 76.0 (B)
Auth0 suits teams that need enterprise SSO on day one.
- Best for: enterprise SSO and SCIM before you pay
- Best agent result: 85 (B) on OpenClaw; tied first on Codex at 80
- Agent assets: 6 of 7 readiness assets, including a local MCP server (
npx @auth0/auth0-mcp-server init), in beta as of November 2026 - Free tier or price: the Free plan includes 1 enterprise connection, self-service SSO and SCIM (pricing)
At a glance
| # | Tool | Score | Best for | Official MCP server |
|---|---|---|---|---|
| 1 | Clerk | 84.6 (B) | Startup and consumer login | Yes, remote |
| 2 | WorkOS | 84.1 (B) | B2B SSO and directory sync | Yes, remote |
| 3 | Supabase | 83.4 (B) | Apps on Supabase Postgres | Yes, remote |
| 4 | Descope | 78.2 (B) | Auth MCP server, free SSO | Yes, remote |
| 5 | Scalekit | 77.8 (B) | SaaS that ships agents | Yes, hosted |
| 6 | Auth0 | 76.0 (B) | Enterprise SSO on a free plan | Yes, local (beta) |
Prices and MCP details are from vendor pages as of November 2026. The full board lists every tool tested.
How we tested
- The task: install the vendor's official Python SDK, send an invitation to leaderboard-test@example.com, list pending invitations as JSON and revoke the one it created, with no raw HTTP calls.
- 12 coding agents each ran it with a live API key in their own sandbox, and every tool got the same task, agents and grader.
- The score is 70% how well the agents did and 30% agent-ready assets like llms.txt, an OpenAPI spec and an MCP server. B is 75 or higher. Full method: methodology.
FAQ
As a startup, what's the best auth API for agents?
Clerk, at 84.6 across 12 coding agents in the October 2026 tests. Its free Hobby plan covers 50,000 monthly retained users per app.
Is there an auth API that Claude Code can set up for B2B login with SSO?
Yes. On Claude Code's API board in October 2026, WorkOS scored 84 (B) and sells SSO and Directory Sync per connection, and Supabase scored 90 (A) with SAML SSO on Pro and above.
As a developer, what's the best auth MCP server for personal agents?
Descope's server ranked first on Claude Code's MCP board in October 2026 with 84 (B), and Clerk's was second with 81 (B).
Tools can be added at devtoolarena.com/add, and teams that want the same runs on their own tasks can use Lightsage Agent Usability.