Model Context Protocol

Learn MCP

Guides to MCP authentication, and fixes for the errors MCP clients report.

Your MCP server one of these, behind one of those

MCP clients

What is calling your server

Claude Code Claude custom connectors ChatGPT connectors Cursor VS Code

Hosts and gates

Where it runs, and what sits in front

Vercel Netlify Kubernetes Azure Container Apps AWS API Gateway Cloudflare Access

Identity providers

Who issues the credential

Microsoft Entra ID Okta Auth0 Keycloak Amazon Cognito

Customer story

Finsolutia launched an MCP server in hours

Finsolutia is a mortgage servicer, about 400 people across Lisbon, Oporto and Madrid. Their REST APIs already had OpenAPI descriptions, so the MCP server was generated from those rather than written by hand. One company's result, not a trend.

We didn't touch a line of code, it's just plug and play. The results were very surprising, in just a couple of hours we had a great result and a fully working MCP Server.

Miguel Madeira CTO & Co-Founder, Finsolutia

From zero to MCP deployment: < 24 hours
Code changes: 0

Read the Finsolutia case study

Topics

Where to start

Topic MCP authentication How callers prove who they are to a remote MCP server, with working code for each method. Methods covered Anthropic-hosted agents API key AWS IAM (SigV4) Client credentials (M2M) Google Cloud IAM Microsoft Entra ID mTLS OAuth 2.1 See all methods

Reference Errors clients report Look up the error your client printed, and fix it on your platform. Includes [mcp-sdk] excluding tool '<name>' from tools/list: invalid x-mcp-header declaration Authorization with the MCP server failed Couldn't reach the MCP server and 10 more See all errors

Reference Glossary What each term means, cited to the RFC or specification section it comes from. Acronyms covered ASM CIMD DCR ID-JAG MRTR PKCE PRM SEP Look up a term

Reference Client and provider compatibility What each MCP client puts on the wire, and what each identity provider supports. Every cell cites a source. Clients covered claude.ai ChatGPT connectors and apps Claude Code Claude Agent SDK Claude Managed Agents Messages API MCP connector OpenAI Responses API mcp tool Microsoft Copilot Studio Codex CLI Gemini CLI and 12 more See both matrices

Ship MCP servers without rebuilding auth

A gateway in front of your MCP servers handles discovery, audience binding, and token validation once — for every server and every client.

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