Clients
The 9 MCP clients with a researched registry entry. Each page has the client's capabilities, how each one is known, the probe's records for it, and its research notes.
| Client | Vendor | Category | Prefers | Last read |
|---|---|---|---|---|
| goose | Block | agent-framework | 2026-07-28 |
2026-08-23 |
| Codex CLI | OpenAI | cli | 2025-06-18 |
2026-08-24 |
| opencode | Anomaly | cli | 2025-11-25 |
2026-08-24 |
| Cline | Cline Bot Inc. | ide | 2025-11-25 |
2026-08-25 |
| fast-agent | Shaun Smith (llmindset) | agent-framework | 2026-07-28 |
2026-08-25 |
| OpenClaw | OpenClaw Foundation | agent-framework | 2025-11-25 |
2026-08-26 |
| Hermes Agent | Nous Research | cli | 2025-11-25 |
2026-11-09 |
| Kilo Code | Kilo Code | ide | 2025-11-25 |
2026-11-10 |
| Google Antigravity | ide | 2026-07-28 |
- goose: Open-source agent from Block, shipping as a desktop app and a CLI from one Rust codebase. Uses rmcp as its MCP client, resolved to 3.1.4.
- Codex CLI: OpenAI's coding agent, shipping as a CLI and an app-server. Rust, using rmcp 3.1.3 as its MCP client through a codex-rmcp-client wrapper crate. Codex also runs as an MCP server, which is a separate code path and not described here.
- opencode: Open-source terminal coding agent, TypeScript on the official MCP TypeScript SDK. Ships a patched copy of SDK 1.29.0, so its transport behaviour is not stock.
- Cline: Open-source coding agent shipping as a VS Code extension and a CLI from one monorepo. Both surfaces use the official TypeScript SDK unpatched, except the CLI's stdio path, which is a hand-written JSON-RPC client fixed at 2024-11-05.
- fast-agent: Python framework and CLI for building and running agents, from the maintainer of the SEP-2640 skills proposal and the HF client telemetry feed. The first client read here that leads with the 2026-07-28 stateless era: it probes server/discover before falling back to the initialize handshake, and behaves differently on each.
- OpenClaw: Multi-channel AI gateway that runs agents across chat surfaces and remote nodes. Two MCP client surfaces: the per-session agent bundle and the headless node host.
- Hermes Agent: Python agent CLI, desktop app and gateway from Nous Research. The second client here on the mcp Python SDK and the counterpart to fast-agent on it: same library, opposite protocol-era default. Hermes leads with the initialize handshake and probes server/discover only when a server rejects it. One MCP client serves every surface.
- Kilo Code: Open-source coding agent for VS Code, JetBrains and the terminal. Now built on opencode, not Cline: the CLI is a fork of opencode's, and the VS Code and JetBrains extensions both spawn
kilo serve, so one MCP client sits behind every surface. Ships a patched SDK 1.32.1 on main; the v2 branch has moved to the split SDK. - Google Antigravity: Google's agentic IDE and CLI, the successor to Gemini CLI for consumer accounts. Closed source, so nothing here is a read. The entry joins Apify's curated record, unchanged since November 2025, to Hugging Face MCP traffic, and the two disagree on protocol revision and elicitation.
The probe has also run clients that have no registry entry yet. Their records are on Tool result handling, verified.