MCP Server Catalog
Chapter 10 of Loop Engineering uses a nervous-system analogy for MCP while keeping its boundary clear: MCP is exchange infrastructure, not judgment, governance, security, or memory. Use the live catalog below to compare current servers, adopters, and capabilities.
Each entry below is verified against the cited upstream source. Rows are grouped by category. Refreshed quarterly; next review 2026-09.
Reference clients and protocol authority
| Vendor / project | What it exposes | Client compatibility | Source | Verified |
|---|---|---|---|---|
| Anthropic - Claude Desktop / Claude Code | Reference MCP client. Configurable via claude_desktop_config.json to connect to any compliant MCP server (filesystem, git, databases, search, etc.). |
n/a - this is the reference client. | modelcontextprotocol.io | 2026-06 |
| MCP specification | The protocol itself: JSON-RPC 2.0 over stdio or HTTP-SSE; resources, tools, prompts, and sampling primitives. | Any compliant client. | spec.modelcontextprotocol.io | 2026-06 |
Vendor adopters (named in the launch announcement)
The following vendors were named in Anthropic's MCP launch announcement (November 25, 2024) as early adopters integrating MCP into their products.
| Vendor / project | What it exposes | Client compatibility | Source | Verified |
|---|---|---|---|---|
| Block | Internal developer-tooling exposure for agentic systems. Named in launch as an early adopter integrating MCP into agentic systems. | Internal Block tooling; per launch announcement. | launch announcement | 2026-06 |
| Apollo | GraphQL schema and operations exposed via MCP server. Named in launch as integrating MCP for AI access to Apollo's GraphQL platform. | Any MCP client. | launch announcement · apollographql.com | 2026-06 |
| Zed | Editor-native MCP client. Zed's assistant panel connects to MCP servers for context-aware code assistance. | n/a - Zed is itself an MCP client surface. | zed.dev · launch announcement | 2026-06 |
| Replit | Workspace and run-environment exposure for AI agents working inside Replit projects. Named in launch as integrating MCP into the Replit AI experience. | Replit AI surfaces. | replit.com · launch announcement | 2026-06 |
| Codeium / Windsurf | IDE MCP client surface for connecting Codeium / Windsurf to compliant MCP servers (filesystem, repo intelligence, custom backends). | Windsurf IDE; per launch announcement. | codeium.com · launch announcement | 2026-06 |
| Sourcegraph | Code intelligence exposed via MCP server (cross-repo search, symbol navigation, definitions, references) for AI assistants. Named in launch. | Any MCP client. | sourcegraph.com · launch announcement | 2026-06 |
Community reference servers (modelcontextprotocol/servers)
The official MCP servers repository hosts a maintained set of reference and community-contributed servers. The catalog grows continuously; the entries below are widely deployed reference servers as of the verified date.
| Server | What it exposes | Notes | Verified |
|---|---|---|---|
| mcp-server-filesystem | Read / write access to a local filesystem subtree. | Path-scope is enforced server-side; the client cannot escape the configured root. | 2026-06 |
| mcp-server-git | Git operations (status, log, diff, blame) on a local repository. | Read-only operations are unscoped; write operations require explicit allow-list. | 2026-06 |
| mcp-server-github | GitHub REST and search APIs (issues, PRs, code search, branches). | Requires a personal access token with appropriate scopes. | 2026-06 |
| mcp-server-postgres | PostgreSQL query interface (schema introspection, parameterized queries). | Connection string is server-side; client sees only the query API surface. | 2026-06 |
| mcp-server-sqlite | SQLite query interface for local .db files. |
Often used for analytics over exported data. | 2026-06 |
| mcp-server-slack | Slack workspace exposure (channels, messages, search). | Requires a Slack bot token; channel scopes are token-controlled. | 2026-06 |
| mcp-server-puppeteer | Headless browser automation (navigate, click, screenshot, evaluate JS). | Side-effect surface is large; the chapter's confirmation-gate discipline applies hard here. | 2026-06 |
How to read this catalog
Two distinctions to keep clean:
- Client vs server - an MCP client is the AI-facing surface (Claude Desktop, Zed, Windsurf, Cursor); an MCP server is the capability the client connects to. Some products are both (a Zed editor is a client, but ships server-side hooks for its own state).
- Spec-listed vs community - the official servers repo hosts reviewed reference implementations; community indexes (such as the awesome-mcp-servers list) aggregate broader contributions of variable maturity.
Verification discipline
Each row is marked with the month it was verified against its upstream source. Quarterly refresh; if a row is older than six months, treat it as a snapshot. Corrections welcome via the errata page.