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mcp-auth-oauth

mcp-auth-oauth is a skill for Claude Code from latestaiagents/agent-skills. It costs 108 tokens per session (1,827 once invoked), scanned A, original, MIT.

A guide to protecting remote MCP servers with OAuth 2.1 and PKCE, which let users sign in and grant limited access without sharing permanent credentials.

In plain words
What is it for?
Use it to add authentication to a multi-user MCP server, migrate from static tokens, or investigate authorization failures.
Why use it?
It replaces hard-coded bearer tokens with a user-based login flow, token renewal, and permission scopes.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code.

Part of the mcp-mastery plugin — 7 skills shipped together , and of latestaiagents

not rated 6repo changed 2d ago A scan 108 tokens original MIT

Good fit Use it to add authentication to a multi-user MCP server, migrate from static tokens, or investigate authorization failures.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/latestaiagents/agent-skills/mcp-auth-oauth
View source ↗ latestaiagents/agent-skills latestaiagents.com
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add latestaiagents/agent-skills --skill mcp-auth-oauth
Clone the repo
git clone --depth 1 https://github.com/latestaiagents/agent-skills

Made for: Claude Code.

Or install mcp-mastery, the plugin that ships this one along with the rest of its 7 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for mcp-auth-oauth

README.md
[![agentmods](https://agentmods.dev/badge/skills/latestaiagents/agent-skills/mcp-auth-oauth/github.svg)](https://agentmods.dev/skills/latestaiagents/agent-skills/mcp-auth-oauth)
Your own site
<a href="https://agentmods.dev/skills/latestaiagents/agent-skills/mcp-auth-oauth"><img src="https://agentmods.dev/badge/skills/latestaiagents/agent-skills/mcp-auth-oauth/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for mcp-auth-oauth

Your own site · 80×15
<a href="https://agentmods.dev/skills/latestaiagents/agent-skills/mcp-auth-oauth"><img src="https://agentmods.dev/badge/skills/latestaiagents/agent-skills/mcp-auth-oauth.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 108 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,827 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00108 $0.01827
Opus 5.5 $0.00043 $0.00731
Sonnet 5.5 $0.00022 $0.00365
Haiku 4.5 $0.00011 $0.00183

Measured 2d ago against content hash ad7ff63ff543, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcp-auth-oauth scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/mcp-mastery/mcp-auth-oauth/SKILL.md · 176 lines

How it starts

The opening of the file, as written. The whole thing — 176 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Auth — OAuth 2.1

Remote MCP servers use OAuth 2.1 + PKCE. Spec-compliant MCP clients discover your authorization server, obtain a client ID without manual setup, and authenticate users in a browser.

Spec status: check the current authorization spec at https://modelcontextprotocol.io/specification/latest/basic/authorization before building. In current revisions, servers MUST publish OAuth Protected Resource Metadata (RFC 9728), clients MUST send the resource parameter (RFC 8707), clients and authorization servers SHOULD support Client ID Metadata Documents for registration, and Dynamic Client Registration (RFC 7591) is deprecated, kept for backwards compatibility. The DCR example below still works with clients that use it; add CIMD support for new servers.

When to Use

  • Building a remote MCP server that serves multiple users
  • Migrating a static-bearer-token server to per-user auth
  • Debugging "401 Unauthorized" or "failed to authenticate" in an MCP client
  • Adding scope-based permission to an MCP server

The Flow (RFC 9728 + RFC 8414 + PKCE)

  1. Client connects to MCP server → server returns 401 with WWW-Authenticate: Bearer resource_metadata="…" pointing to its Protected Resource Metadata
  2. Client fetches that metadata → learns the authorization server, then fetches /.well-known/oauth-authorization-server (or OpenID discovery) → gets authorization_endpoint, token_endpoint, and optionally registration_endpoint
  3. Client obtains a client_id: a Client ID Metadata Document URL (preferred), a pre-registered ID, or Dynamic Client Registration (deprecated fallback)
  4. Client opens browser to authorization_endpoint with PKCE challenge → user approves
  5. Client exchanges code at token_endpoint → receives access + refresh tokens
  6. Client retries MCP request with Authorization: Bearer <token>

No manual app registration for the user. They just click "Allow" in a browser.

Server-Side Requirements

1. Return discovery metadata

Read the full file on GitHub · 176 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago Changed · +2 lines ad7ff63ff543
  2. 2mo ago First seen · 174 lines · 108 tokens per session scan A 6636336c7daf

Subscribe to this mod's changes

mcp-auth-oauth is a skill published in the GitHub repository latestaiagents/agent-skills (6 stars, last pushed 2d ago), licensed MIT. It adds 108 tokens to every session and 1,827 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Building agentsSecurityagentic-aiagentic-ragagentic-workflowagentshubagentskillsai
Related

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mcp-auth-oauth next to 6 skills from other repositories
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