130 pages for stderr.

Recipes Model Context Protocol · in the page docs/2026-07-28/tools/inspector/recipes …--cwd ~/projects/my-server \ node build/index.js ``` The server's `stderr` lands in the **Console** tab (web) or the Console tab (`o`, TUI), which is where most stdio servers put their diagnostics,… Security Model Context Protocol · in the page docs/2026-07-28/tools/inspector/security …key that file is **unencrypted**. > > The only signs are a warning on stderr when the store is selected and a footer in the web client's settings dialogs. Treat that as a risk, not just a configurati… TUI client Model Context Protocol · in the page docs/2026-07-28/tools/inspector/tui …ication/latest/basic/transports.md) servers. | | **Console** | `o` | `stderr` from a connected stdio server process. | The accelerators avoid collisions rather than always taking the first letter: **… Web client Model Context Protocol · in the page docs/2026-07-28/tools/inspector/web …ders, bodies. | | **Console** | stdio servers | The server process's `stderr`. | **Network** and **Console** never appear together. Legacy and modern eras are described in [Protocol eras](https://mod… Build an MCP server Model Context Protocol · in the page docs/draft/develop/build-server …ices > > * Use the standard library `logging` module, which writes to stderr. > * Create one logger per module with `logging.getLogger(__name__)` and call it from your tools. > > ### Quick Examples >… Connect to local MCP servers Model Context Protocol · in the page docs/draft/develop/connect-local-servers …lures. > > * Files named `mcp-server-SERVERNAME.log` will contain the stderr output from the named server. Stdio servers may use stderr for all their logging, so these files are not limited to errors.… Architecture overview Model Context Protocol · in the page docs/draft/learn/architecture …debugging and monitoring purposes. New implementations should log to `stderr` (stdio transport) or use OpenTelemetry. For more details about client primitives see [client concepts](https://modelconte… Debugging Model Context Protocol · in the page docs/draft/tools/debugging …should be your first stop. 2. **Server logging**: structured logs to stderr (stdio transport) or via [OpenTelemetry](https://opentelemetry.io/) (all transports). [Logging](https://modelcontextp… Authorization Model Context Protocol · in the page docs/draft/tools/inspector/authorization …403` surfaces as an error instead. In the **CLI**, step-up prompts on stderr: ``` Proceed with step-up authorization? [y/N] ``` Answer **y** to continue. Piped input works (`echo y | ...`), as long… CLI client Model Context Protocol · in the page docs/draft/tools/inspector/cli …. | On any non-zero exit the CLI also writes a **single JSON line to stderr**: ```json theme={null} { "error": { "code": "auth_required", "message": "Unauthorized", "status": 401,… Configuration and flags Model Context Protocol · in the page docs/draft/tools/inspector/configuration …put (the same as `--plain`), and the sign-in prompt the CLI writes to stderr. | ### Web backend environment variables | Variable | Effect | | - | - | | `MCP_INSPECTOR_API_TOKEN` | Pin the [session t… mcpdo connection client Model Context Protocol · in the page docs/draft/tools/inspector/mcpdo …hoc target. | When a browser sign-in is needed and neither stdin nor stderr is a TTY (and `MCP_AUTO_OPEN_ENABLED` is not forced on), `connect` exits `0` immediately with `pendingAuth: true` and an `a… Protocol eras Model Context Protocol · in the page docs/draft/tools/inspector/protocol-eras …ig test-servers/configs/<name>.json ``` The server prints its URL on stderr. If the config's port is already in use, it binds the next free port, so use the printed URL rather than assuming the port.… Recipes Model Context Protocol · in the page docs/draft/tools/inspector/recipes …--cwd ~/projects/my-server \ node build/index.js ``` The server's `stderr` lands in the **Console** tab (web) or the Console tab (`o`, TUI), which is where most stdio servers put their diagnostics,… Security Model Context Protocol · in the page docs/draft/tools/inspector/security …key that file is **unencrypted**. > > The only signs are a warning on stderr when the store is selected and a footer in the web client's settings dialogs. Treat that as a risk, not just a configurati… TUI client Model Context Protocol · in the page docs/draft/tools/inspector/tui …ication/latest/basic/transports.md) servers. | | **Console** | `o` | `stderr` from a connected stdio server process. | The accelerators avoid collisions rather than always taking the first letter: **… Web client Model Context Protocol · in the page docs/draft/tools/inspector/web …ders, bodies. | | **Console** | stdio servers | The server process's `stderr`. | **Network** and **Console** never appear together. Legacy and modern eras are described in [Protocol eras](https://mod… SEP-2577: Deprecate Roots, Sampling, and Logging Model Context Protocol · in the page seps/2577-deprecate-roots-sampling-and-logging …ocol: * **Overlapping infrastructure**: Standard logging mechanisms (stderr for stdio transports, OpenTelemetry for structured observability) are mature, widely adopted, and better suited to logg… Transports Model Context Protocol · in the page specification/2024-11-05/basic/transports …nes. * The server **MAY** write UTF-8 strings to its standard error (`stderr`) for logging purposes. Clients **MAY** capture, forward, or ignore this logging. * The server **MUST NOT** write anythin… Transports Model Context Protocol · in the page specification/2025-03-26/basic/transports …nes. * The server **MAY** write UTF-8 strings to its standard error (`stderr`) for logging purposes. Clients **MAY** capture, forward, or ignore this logging. * The server **MUST NOT** write anythin… Transports Model Context Protocol · in the page specification/2025-06-18/basic/transports …nes. * The server **MAY** write UTF-8 strings to its standard error (`stderr`) for logging purposes. Clients **MAY** capture, forward, or ignore this logging. * The server **MUST NOT** write anythin… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …nes. * The server **MAY** write UTF-8 strings to its standard error (`stderr`) for any logging purposes including informational, debug, and error messages. * The client **MAY** capture, forward, or… Key Changes Model Context Protocol · in the page specification/2025-11-25/changelog …Minor changes 1. Clarify that servers using stdio transport may use stderr for all types of logging, not just error messages (PR [#670](https://github.com/modelcontextprotocol/modelcontextprotocol/p… stdio Model Context Protocol · in the page specification/2026-07-28/basic/transports/stdio …ntain embedded newlines. * The server **MAY** write UTF-8 strings to `stderr` for any logging purposes including informational, debug, and error messages. * The client **MAY** capture, forward, or i… Key Changes Model Context Protocol · in the page specification/2026-07-28/changelog …grate directly with LLM provider APIs instead of Sampling; log to `stderr` (stdio) or use OpenTelemetry instead of Logging. 2. Reclassify the HTTP+SSE transport (deprecated since protocol versi… Deprecated Features Model Context Protocol · in the page specification/2026-07-28/deprecated …textprotocol/modelcontextprotocol/pull/2577) | `2026-07-28` | Log to `stderr` for stdio transports; use [OpenTelemetry](https://opentelemetry.io/) for observability | First revision released on or aft… Logging Model Context Protocol · in the page specification/2026-07-28/server/utilities/logging …adopt it; existing implementations **SHOULD** migrate to logging to `stderr` > for stdio transports, or to [OpenTelemetry](https://opentelemetry.io/) for > structured observability. See the [deprecat… stdio Model Context Protocol · in the page specification/draft/basic/transports/stdio …ntain embedded newlines. * The server **MAY** write UTF-8 strings to `stderr` for any logging purposes including informational, debug, and error messages. * The client **MAY** capture, forward, or i… Deprecated Features Model Context Protocol · in the page specification/draft/deprecated …textprotocol/modelcontextprotocol/pull/2577) | `2026-07-28` | Log to `stderr` for stdio transports; use [OpenTelemetry](https://opentelemetry.io/) for observability | First revision released on or aft… Logging Model Context Protocol · in the page specification/draft/server/utilities/logging …adopt it; existing implementations **SHOULD** migrate to logging to `stderr` > for stdio transports, or to [OpenTelemetry](https://opentelemetry.io/) for > structured observability. See the [deprecat…