Connect Claude Code to tools via MCP changedmcp
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7979When configuring MCP servers via JSON in `.mcp.json`, `~/.claude.json`, or `claude mcp add-json`, the `type` field accepts `streamable-http` as an alias for `http`. The MCP specification uses the name `streamable-http` for this transport, so configurations copied from server documentation work without modification.
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81A JSON entry that has a `url` but no `type` is a configuration error, because Claude Code reads an entry with no `type` as a stdio server. Claude Code skips that server and reports `MCP server "<name>" has a "url" but no "type"; add "type": "http" (or "sse" / "ws") to this entry`. Before v2.1.202, Claude Code reported this misconfiguration as `command: expected string, received undefined`.
81A JSON entry that has a `url` but no `type` is a configuration error, because Claude Code reads an entry with no `type` as a stdio server. Claude Code skips that server and reports `MCP server "<name>" has a "url" but no "type"; add "type": "http" (or "sse" / "ws") to this entry`.
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8383Only an SDK host application, such as an [Agent SDK](/docs/en/agent-sdk/mcp) application or the [desktop app](/docs/en/desktop), 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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113113Claude Code sets `CLAUDE_PROJECT_DIR` in the spawned server's environment to the project root, so your server can resolve project-relative paths without depending on the working directory. This is the same directory hooks receive in their `CLAUDE_PROJECT_DIR` variable. Read it from inside your server process, for example `process.env.CLAUDE_PROJECT_DIR` in Node or `os.environ["CLAUDE_PROJECT_DIR"]` in Python.
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115`CLAUDE_PROJECT_DIR` is the stable project root and doesn't change when you add or remove working directories mid-session. A server that limits its own filesystem access to a set of allowed directories should implement the MCP `roots/list` request instead. Claude Code answers `roots/list` with the session's launch directory plus every [additional working directory](/docs/en/permissions#working-directories) you've granted with `--add-dir`, `/add-dir`, or the `additionalDirectories` setting. Claude Code sends `notifications/roots/list_changed` when that set changes. Before v2.1.203, `roots/list` returned only the launch directory and Claude Code didn't send `notifications/roots/list_changed`.
115`CLAUDE_PROJECT_DIR` is the stable project root and doesn't change when you add or remove working directories mid-session. A server that limits its own filesystem access to a set of allowed directories should implement the MCP `roots/list` request instead. Claude Code answers `roots/list` with the session's launch directory plus every [additional working directory](/docs/en/permissions#working-directories) you've granted with `--add-dir`, `/add-dir`, or the `additionalDirectories` setting. Claude Code sends `notifications/roots/list_changed` when that set changes.
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117117This variable is set in the server's environment, not in Claude Code's own environment, so referencing it via `${VAR}` expansion in the `command` or `args` of a project-scoped `.mcp.json` entry or a local- or user-scoped server entry in `~/.claude.json` requires a default such as `${CLAUDE_PROJECT_DIR:-.}`. Plugin-provided MCP configurations substitute `${CLAUDE_PROJECT_DIR}` directly and don't need the default.
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429429The per-server `timeout` is a hard wall-clock limit per tool call, and progress notifications from the server don't extend it. Values below 1000 are ignored and fall through to `MCP_TOOL_TIMEOUT`, or to its default of about 28 hours when that variable is unset. For an HTTP, SSE, or [claude.ai connector](/docs/en/mcp#use-mcp-servers-from-claude-ai) server there is also a second, per-request timer that covers each request through to the server's first response byte. Claude Code sets that timer to the greatest of three values: 60 seconds, the tool timeout that applies to the server, and `MCP_TIMEOUT`. The 28-hour default of an unset `MCP_TOOL_TIMEOUT` doesn't enter that comparison, and a value below 60 seconds doesn't shorten the timer. Stdio and WebSocket servers have no per-request timer.
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431A per-server `timeout` of at least 1000 also acts as a floor on the idle timeout described below: Claude Code never aborts that server's tool calls for idleness sooner than the per-server `timeout`. Requires Claude Code v2.1.203 or later.
431A per-server `timeout` of at least 1000 also acts as a floor on the idle timeout described below: Claude Code never aborts that server's tool calls for idleness sooner than the per-server `timeout`.
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433A tool call to an MCP server that sends no response and no progress notification for the idle window aborts with an error instead of waiting for the wall-clock limit. The idle timeout applies to every server type except IDE servers and SDK in-process servers. The idle window defaults to five minutes for HTTP, SSE, WebSocket, and [claude.ai connector](#use-mcp-servers-from-claude-ai) servers, and to 30 minutes for stdio servers. Before v2.1.203, stdio servers were exempt from the idle timeout.
433A tool call to an MCP server that sends no response and no progress notification for the idle window aborts with an error instead of waiting for the wall-clock limit. The idle timeout applies to every server type except IDE servers and SDK in-process servers. The idle window defaults to five minutes for HTTP, SSE, WebSocket, and [claude.ai connector](#use-mcp-servers-from-claude-ai) servers, and to 30 minutes for stdio servers.
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435435Set the [`CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT`](/docs/en/env-vars) environment variable in milliseconds to change the idle window, or set it to `0` to disable the check.
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762762* For a server whose `Authorization` header you configured, in `headers` or through a [`headersHelper`](#use-dynamic-headers-for-custom-authentication), a `401` or `403` while connecting doesn't flag the server, because the credential to fix is the one you configured. Claude Code reports the connection as failed instead. If you set that header from a `${VAR}` reference, check whether that variable is one Claude Code [reads as empty](#credential-variables-that-read-as-empty).
763763* For a connector [delivered to a cloud session](#how-connectors-reach-claude-code), Claude Code doesn't run a sign-in flow, because the session's proxy authenticates to the connector with the authorization you granted in claude.ai. When a connector there needs authorizing again, reconnect it at [claude.ai/customize/connectors](https://claude.ai/customize/connectors) rather than from the session.
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765When a request to an OAuth server you already signed in to returns `401 Unauthorized`, Claude Code refreshes the stored token, reconnects, and retries the request once. It flags the server in `/mcp` only if that retry also fails. Before v2.1.206, a token refresh that failed for a transient reason, such as a network error, flagged an OAuth server as needing authentication for the rest of the session even though its refresh token was still valid.
765When a request to an OAuth server you already signed in to returns `401 Unauthorized`, Claude Code refreshes the stored token, reconnects, and retries the request once. It flags the server in `/mcp` only if that retry also fails.
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767767When the server rejects the stored refresh token, Claude Code immediately shows a notice pointing at `/mcp`. Open `/mcp` and select **Re-authenticate** on the server to sign in again before the next tool call fails.
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1112Server names added through `claude mcp` commands can contain only letters, numbers, hyphens, and underscores. Claude Desktop doesn't apply that restriction, so a Claude Desktop server whose name contains any other character, such as a space, can't be imported. The import reports each name it rejects and still imports the other servers you selected. Before v2.1.205, the first invalid name stopped the import and none of the selected servers were added.
1112Server names added through `claude mcp` commands can contain only letters, numbers, hyphens, and underscores. Claude Desktop doesn't apply that restriction, so a Claude Desktop server whose name contains any other character, such as a space, can't be imported. The import reports each name it rejects and still imports the other servers you selected.
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