Connect Claude Code to tools via MCP changedmcp
Nearest release: v2.1.312, published under an hour before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
Upstream edited this page at 27 Oct 2026 19:25 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 27 Oct 2026 19:37 UTC.
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##### Connection failures and unconfigured servers
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8181Only an SDK host application, such as an [Agent SDK](https://code.claude.com/docs/en/agent-sdk/mcp.md) application or the [desktop app](https://code.claude.com/docs/en/desktop.md), can register an in-process `"type": "sdk"` server. Claude Code skips a `"type": "sdk"` entry in `.mcp.json`, `~/.claude.json`, or settings and reports `Skipped — MCP server "<name>" declares type "sdk", which only an SDK host application can register`.
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83In `--output-format stream-json` runs, Claude Code also reports a skipped `--mcp-config` entry in the `system/init` event's [`mcp_server_errors` field](https://code.claude.com/docs/en/headless#stream-responses), so scripts can detect that the server never loaded. This requires Claude Code v2.1.219 or later.
83> [!NOTE]
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85> In `--output-format stream-json` runs, Claude Code also reports a skipped `--mcp-config` entry in the `system/init` event's [`mcp_server_errors` field](https://code.claude.com/docs/en/headless#stream-responses), so scripts can detect that the server never loaded.
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8587### Option 2: Add a remote SSE server
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273275When you select **Disable** or **Clear authentication** from a server's menu in `/mcp`, Claude Code also discards that server's cache entry. **Reconnect** discards it too on a connected or failed server; on a `cached` server, **Reconnect** connects the server now and keeps the entry. The next time Claude Code connects to the server after discarding the entry, it fetches the tool list from the server instead of from the cache.
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275When a server's status is `✘ Failed to connect`, `claude mcp list` appends the failure detail to that status line, and `claude mcp get <name>` shows it on an `Issue:` line: the HTTP status or error code, plus any error text the server returned. The server's detail view in `/mcp` includes the same server-reported text in its `Issue:` row. Claude Code redacts credential-like text from this detail and never includes the expanded server URL, which can carry secrets. Claude Code appends no detail to a `✘ Connection error` status, because the exception text it would print there can embed that URL. Before v2.1.219, both commands showed only the bare failure status, without the status code or the server's error text.
277##### Connection failures and unconfigured servers
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279When a server's status is `✘ Failed to connect`, `claude mcp list` appends the failure detail to that status line, and `claude mcp get <name>` shows it on an `Issue:` line. The detail is the HTTP status or error code, plus any error text the server returned. The server's detail view in `/mcp` includes the same server-reported text in its `Issue:` row.
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281Claude Code redacts credential-like text from this detail and never includes the expanded server URL, which can carry secrets. Claude Code appends no detail to a `✘ Connection error` status, because the exception text it would print there can embed that URL.
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277283When you complete authentication from `/mcp` and the connection still fails with an HTTP status or a transport error code, Claude Code adds that code and the origin of the server's URL to the message it prints after the attempt. The origin is the scheme and host, plus the port when the URL names one, such as `https://mcp.example.com`.
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