Learn MCP

A developer introduction to MCP roles, tools, resources, prompts, transports, and the two protocol lifecycle eras.

6 min read·Newcomer

How stdio and Streamable HTTP servers differ in sessions, authentication, deployment, CORS, and compatibility.

7 min read·Practitioner

A decision framework for choosing MCP, a normal API, direct function calling, client-specific apps or skills, or an integration gateway.

8 min read·Newcomer

What the Model Context Protocol is, what problem it solves, and what happens when an AI assistant uses a connected server, explained without code.

5 min read·Newcomer

Six practical uses of MCP servers, from searching your own documents to coding agents and unattended automation, each with a real public server and its honest limits.

4 min read·Newcomer

What a connected MCP server can see and do, how tool poisoning and prompt injection work, what OAuth consent and tool approvals protect, and how to vet a server before you connect it.

6 min read·Newcomer

How MCP relates to ordinary APIs and to model function calling, with a comparison table and guidance on when each one is the right layer.

5 min read·Practitioner

Forty-one Model Context Protocol terms in alphabetical order, from API key to transport, each defined in one or two sentences and linked by anchor.

7 min read·Newcomer

The Model Context Protocol from its November 2024 launch to the stateless 2026-07-28 revision: governance, adoption, and what each specification revision changed for users.

4 min read·Newcomer

An honest comparison of five MCP testing tools on install, remote OAuth, browser CORS evidence, shareable reports, catalogs, CI and price, with what each does best.

6 min read·Practitioner

Eight MCP testing tools, from the official Inspector and conformance suite to MCPJam, Glama, Postman, two compliance CLIs and mcptest.io, compared on OAuth, CORS evidence, output validation, reports, CI, price and license.

11 min read·Practitioner

Two zero-install browser inspectors for remote MCP servers compared on connection path, OAuth, CORS evidence, report sharing and badges, catalog, diagnostics, structured output, price and openness.

6 min read·Practitioner

Turn an MCP server assessment into an approval decision with recorded evidence, a limited pilot, organisation allowlisting and a repeatable audit trail.

7 min read·Practitioner

A client-oriented walkthrough for testing an authless or OAuth-protected Streamable HTTP endpoint and diagnosing the first connection.

8 min read·Newcomer

Compare the documented transports, authentication paths, capabilities, configuration, and approval controls in six widely used MCP clients.

11 min read·Practitioner

Follow the MCP authorization sequence from a 401 challenge through resource and issuer discovery, PKCE and client registration, token exchange, and retry.

10 min read·Practitioner

Step-by-step setup for remote MCP servers in claude.ai custom connectors, Claude Desktop and Claude Code, with the plan differences and the real failure modes for each.

7 min read·Newcomer

Add a custom MCP server to ChatGPT from Plugins, understand why the option is missing on many accounts, and know when deep research needs search and fetch tools.

6 min read·Newcomer

Configure a remote MCP server in Cursor's mcp.json, complete OAuth, and fix the Client Closed, Loading tools and No tools found states from the MCP Logs.

5 min read·Practitioner

Add a remote HTTP MCP server for GitHub Copilot in VS Code at workspace or user level, complete OAuth, and fix the sign-in that never starts.

5 min read·Practitioner

Remote MCP setup for Windsurf (now Devin Desktop), Gemini CLI and OpenAI Codex, including which transport each key selects and when you need the mcp-remote bridge.

6 min read·Practitioner

Eight checks, in order, for an MCP server that answers 401 in Claude, ChatGPT, Cursor, VS Code or any other client, with what the playground shows when each one is the cause.

9 min read·Practitioner

When a client shows the server as connected but lists no tools, read the raw JSON-RPC exchange to tell a missing capability, a failed tools/list, a lost session, a version mismatch, caching and auth-gated listing apart.

6 min read·Practitioner

Add a remote MCP server to Zed's context_servers setting, sign in with OAuth or pass a header, control which tools the agent may call, and fix the failures Zed users report.

5 min read·Practitioner

Add a remote MCP server to AI Assistant in IntelliJ IDEA, PyCharm, and the other JetBrains IDEs, work around the missing OAuth and header support with a tested mcp-remote bridge, and tell AI Assistant apart from Junie and the IDE's own MCP server.

5 min read·Practitioner

Add a remote MCP server to Copilot CLI with copilot mcp add or mcp-config.json, sign in with OAuth or pass a header from your environment, and configure the same server for Copilot cloud agent with COPILOT_MCP_ secrets.

6 min read·Practitioner

Connect Supabase, Airtable or Notion to your assistant, start with a small read-only question, and check permissions and results in mcptest.io before trusting the answers.

6 min read·Newcomer

Check Claude and ChatGPT mobile and voice support as of October 2026, distinguish custom-server setup from plugin use, and test a small read action before going hands-free.

5 min read·Newcomer

A step-by-step guide to validating stateless 2026 and stateful 2025 remote MCP servers, in the playground and from the command line.

7 min read·Practitioner

Design focused tools and schemas, control context cost, choose a deployment state model, and build observable, rate-limited failure handling.

13 min read·Expert

Evaluate a server's publisher, code and hosting, permissions, authentication, write behavior, evidence, logging, and revocation before connecting it.

9 min read·Practitioner

What a client does on connect, the order mcptest checks it in, how to read the release decision, and how to run the same gate in CI.

8 min read·Practitioner

Move a stdio server to Streamable HTTP in TypeScript or Python, choose stateless 2026 or stateful 2025 behavior, add authorization, and update client configuration.

9 min read·Practitioner

Deploy a Streamable HTTP MCP server to Cloudflare Workers, Vercel, or a Node or Python host behind a reverse proxy, and avoid the platform defaults that show up as transport diagnostics.

8 min read·Practitioner

A practical loop for building a remote MCP server with a coding agent, with a starting prompt, an AGENTS.md or CLAUDE.md validation section, a way to feed mcptest findings back, and the mistakes agents make most.

7 min read·Practitioner

The exact Allow-Origin, Allow-Methods, Allow-Headers, Expose-Headers, and Max-Age values a remote MCP server needs for browser clients, how the preflight works, and tested examples for Express, Hono, Cloudflare Workers, and FastAPI.

9 min read·Practitioner

The Accept rule, request and response content types, and GET stream optionality in Streamable HTTP, with measured TypeScript and Python SDK behavior and the fix for each status.

7 min read·Practitioner

Declare an outputSchema, return structuredContent alongside content, understand what clients validate and which JSON Schema dialect applies, avoid the common violations, and read how mcptest reports a contract break.

7 min read·Practitioner

Publish a SEP-2127 Server Card at your endpoint, list it in an AI Catalog at /.well-known/ai-catalog.json, serve OAuth metadata clients can read, and publish to the official MCP Registry, with copy-paste examples and a free checker.

8 min read·Practitioner

Clients cache tools/list, so a deploy that changes a tool can break agents that still hold the old schema. Which changes break callers, which only change behavior, why list_changed does not save a stateless server, and how to version and ship changes safely.

9 min read·Practitioner

A complete, tested Express server for MCP with the official SDK v2 adapters, Host and Origin checks, CORS, an OAuth bearer check against a hosted identity provider, and the result mcptest reports for it.

7 min read·Practitioner

One tested Hono file that serves MCP with the SDK v2 adapter, CORS, and an OAuth bearer check, and runs unchanged on Node.js, Bun, and Cloudflare Workers, with the runtime-specific pitfalls for each.

6 min read·Practitioner

A complete, tested FastAPI app that mounts the Python SDK's MCPServer with stateless Streamable HTTP, Host and Origin checks, CORS, and a JWT token verifier for a hosted identity provider, plus what mcptest reported for it.

5 min read·Practitioner

A tested Next.js App Router MCP server built with mcp-handler 2.x, with OAuth through withMcpAuth, the protected resource metadata route, Origin checks and CORS that mcp-handler leaves to you, and what mcptest reported for it.

6 min read·Practitioner

A tested Worker built with createMcpHandler from the agents package, with Host and Origin checks, CORS for several origins, an OAuth bearer check for a hosted identity provider, why GET /mcp answers 405 (cloudflare/agents#403), and what mcptest reported.

7 min read·Practitioner

The three ways to protect a remote MCP server, tested code for an API key gate and an OAuth resource server, the settings WorkOS AuthKit, Auth0, and Stytch need, and which clients can use each pattern.

8 min read·Practitioner

Run a tested stateless MCP sample on Vercel Functions, configure duration and browser CORS, and check production domains, cold starts and SSE in mcptest.io.

7 min read·Practitioner

Run a stateless MCP Lambda adapter locally, deploy a RESPONSE_STREAM function URL, and understand API Gateway streaming, payload limits, timeouts and browser CORS.

8 min read·Practitioner

Deploy a tested stateless MCP container to Cloud Run, account for scale-to-zero, request timeouts and best-effort session affinity, then check CORS and SSE in mcptest.io.

7 min read·Practitioner

Run a tested stateless MCP container on Fly Machines, configure autostop, proxy idle timeouts and custom domains, then verify browser CORS and SSE on mcptest.io.

7 min read·Practitioner

Configure Auth0 for MCP with protected resource metadata, resource audience checks, PKCE and CIMD or DCR, including October 2026 Early Access and tenant limitations.

7 min read·Practitioner

Use Clerk as an MCP authorization server with CIMD or DCR, protected resource metadata, explicit OAuth-token verification and scope checks, and an audience-binding compatibility gate.

7 min read·Practitioner

Configure WorkOS AuthKit and Connect for MCP with CIMD, resource indicators, protected resource metadata and exact JWT audience checks, then test OAuth on mcptest.io.

6 min read·Practitioner

Use Stytch Connected Apps for MCP OAuth with CIMD or DCR, protected resource metadata, public-client PKCE, custom audience checks and explicit resource-binding limitations.

7 min read·Practitioner

Gate a remote MCP deploy on client compatibility and tool changes against the last release, with a readable PR comment and optional public report.

5 min read·Practitioner

Diagnose stale MCP sessions after restarts and replica changes, choose durable session ownership or stateless HTTP, and actively test recovery before release.

7 min read·Practitioner

Diagnose an OAuth resource identity mismatch, compare the endpoint path with protected-resource metadata, and decide whether the client configuration or server must change.

5 min read·Practitioner

Fix rejected VS Code MCP redirect URIs and trace the case where an OAuth page opens but connecting fails, from registration to token exchange.

6 min read·Practitioner

Trace failed MCP OAuth discovery from the challenge to issuer metadata, separating refresh failures, wrong paths and browser CORS.

5 min read·Practitioner

Resolve incompatible MCP OAuth client registration by distinguishing missing DCR, pre-registered client configuration and CIMD support.

5 min read·Practitioner

Find the stage rejecting an MCP OAuth callback and align registered, advertised and requested redirect URIs without weakening validation.

5 min read·Practitioner

Separate legacy SSE routing failures from optional Streamable HTTP GET failures and stale sessions using the request method and response body.

5 min read·Practitioner

Decode the HTTP status and response behind a Streamable HTTP POST error to distinguish routing, authentication, media types and gateway failures.

5 min read·Practitioner

Diagnose truncated MCP streams, idle proxy deadlines and premature response cleanup, and distinguish normal stream completion from lost replies.

5 min read·Practitioner

Trace closed MCP connections to session recovery, process failures or dropped streams without assuming that the generic code identifies a server bug.

5 min read·Practitioner

Distinguish MCP request deadlines from connection setup, lost initialization replies and gateway timeouts, with bounded SDK timeout and progress examples.

5 min read·Practitioner

Repair MCP Host allowlists behind Docker and reverse proxies while retaining DNS rebinding protection, with Python and TypeScript SDK examples.

5 min read·Practitioner

Find exact MCP client errors by symptom, then diagnose OAuth discovery, registration, Host rejection, HTTP routing, lost streams and request timeouts.

8 min read·Practitioner

What changed in each MCP revision from 2024-11-05 to 2026-07-28, how clients negotiate and fall back between them, and what stateless means in 2026.

7 min read·Practitioner

Every HTTP header a remote MCP server and client exchange over Streamable HTTP, with direction, versions, example values, failure symptoms and the mcptest diagnostic that fires.

8 min read·Practitioner

JSON-RPC 2.0 reserved codes, MCP-defined codes from -32002 to -32042, the HTTP status each maps to on Streamable HTTP, and isError tool results versus protocol errors.

7 min read·Practitioner

Reference for MCP authorization covering RFC 9728 and RFC 8414 discovery, PKCE S256, CIMD versus dynamic registration, RFC 8707 audience, step-up, refresh, iss validation, confused deputy, and what a browser client can do.

8 min read·Expert

Each mcptest diagnostic id, from transport.accept-header-406 to tool.output-contract-violation, with what was observed, severity, release impact, cause, fixes for three stacks, and the reports behind it.

10 min read·Practitioner

Which MCP clients connect to remote servers, over which transports, with which OAuth registration and static credentials, and what each one cannot do, with a verification date on every row.

9 min read·Practitioner

MCP changes from 2026-09-20 to 2026-10-20: the Server Cards SEP is final, six official SDKs shipped releases, and Claude connectors and Devin Desktop now negotiate 2026-07-28.

7 min read·Practitioner