# canimcp

> Which MCP clients support what, how each claim is known, and research notes on the parts a support matrix cannot express.

canimcp is a registry of Model Context Protocol clients. A capability carries evidence, and each piece of evidence has a tier (`declared`, `verified`, `observed`, `read`) and the protocol revision it applies to. Tiers are not ranked and can disagree.

## When to use this

- Before relying on an MCP feature in a server, check which clients implement it and at which protocol revision.
- To find out what a client does with a tool result: which of `content` and `structuredContent` reaches the model.
- To see where a client's declared capabilities, its source and its observed traffic disagree.

For one client, fetch `https://canimcp.io/data/clients/<id>.json` or its page below. Every page is Markdown at the URL with `.md` appended, and at the page URL with `Accept: text/markdown`. Nothing here needs authentication.

## Clients

- [goose](https://canimcp.io/clients/goose.md): 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](https://canimcp.io/clients/openai-codex.md): 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](https://canimcp.io/clients/opencode.md): 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](https://canimcp.io/clients/cline.md): 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](https://canimcp.io/clients/fast-agent.md): 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...
- [OpenClaw](https://canimcp.io/clients/openclaw.md): 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](https://canimcp.io/clients/hermes-agent.md): 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....
- [Kilo Code](https://canimcp.io/clients/kilocode.md): 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...
- [Google Antigravity](https://canimcp.io/clients/antigravity.md): 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.
- [All clients](https://canimcp.io/clients/llms.txt): the section index

## Across clients

- [Tool result handling, verified](https://canimcp.io/tool-results.md): what reached the model when each client called a fixture tool; links to one record page per client
- [Capabilities observed in traffic](https://canimcp.io/observed.md): capabilities clients declare in real traffic, by protocol revision

## Research notes

- [Research notes](https://canimcp.io/research/index.md): 38 notes, each with a one-paragraph summary
- [Research notes index](https://canimcp.io/research/llms.txt): the section index

## Data

- [Client registry](https://canimcp.io/data/clients.json): every researched client in one JSON file
- [Client index](https://canimcp.io/data/clients/index.json): ids, titles and the per-client JSON URLs
- [Capability lifecycle](https://canimcp.io/data/spec-versions.json): each capability across protocol revisions
- [Observed telemetry](https://canimcp.io/data/observed/hf-mcp-clients.json): the feed behind the observed tier
- Probe records per client: `https://canimcp.io/data/verified/<client>.json`

## Schemas

- [client-registry.json](https://canimcp.io/schemas/client-registry.json)
- [research-note.json](https://canimcp.io/schemas/research-note.json)
- [verified-evidence.json](https://canimcp.io/schemas/verified-evidence.json)
- [observed-evidence.json](https://canimcp.io/schemas/observed-evidence.json)

## Optional

- [About](https://canimcp.io/about.md): where the data comes from, the licence, and how to report a correction
- [Source repository](https://github.com/olaservo/canimcp): the registry, the probe and its captures