MCP Inspector changeddocs/draft/tools/inspector
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33> Interactive developer tooling for testing and debugging MCP servers, in the browser, on the command line, and in the terminal
44
5The [MCP Inspector](https://github.com/modelcontextprotocol/inspector) is the reference developer tool for testing and debugging [MCP servers](/docs/draft/learn/server-concepts). It ships as a single package, `@modelcontextprotocol/inspector`, providing **three clients behind one binary**:
5The [MCP Inspector](https://github.com/modelcontextprotocol/inspector) is the reference developer tool for testing and debugging [MCP servers](/docs/draft/learn/server-concepts.md). It ships as a single package, `@modelcontextprotocol/inspector`, providing **three clients behind one binary**:
66
77| Client | Invocation | What it's for |
88| - | - | - |
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1010| **CLI** | `npx @modelcontextprotocol/inspector --cli` | A scriptable, machine-readable client for CI, shell pipelines, and coding agents. |
1111| **TUI** | `npx @modelcontextprotocol/inspector --tui` | An interactive terminal UI, for when a browser isn't available or wanted. |
1212
13All three are built on the same shared core, so a connection behaves identically across them: the same transports, the same configuration files, the same OAuth state on disk, and the same [protocol-era](/docs/draft/tools/inspector/protocol-eras) negotiation (legacy vs. modern 2026-07-28).
13All three are built on the same shared core, so a connection behaves identically across them: the same transports, the same configuration files, the same OAuth state on disk, and the same [protocol-era](/docs/draft/tools/inspector/protocol-eras.md) negotiation (legacy vs. modern 2026-07-28).
1414
15The package also installs **`mcpdo`**, an experimental [connection client](/docs/draft/tools/inspector/mcpdo) that connects to a server once and keeps it open across many commands, on the same core.
15The package also installs **`mcpdo`**, an experimental [connection client](/docs/draft/tools/inspector/mcpdo.md) that connects to a server once and keeps it open across many commands, on the same core.
1616
1717
1818
19The MCP Inspector web client after a tool call, with the monitoring sidebar pinned and widened so the JSON-RPC exchange stays readable while you work.
20
1921## Quickstart
2022
2123The Inspector requires **Node 22.19.0 or newer** and runs directly through `npx`. No installation is required:
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3032npx @modelcontextprotocol/inspector
3133```
3234
33The command prints a URL carrying a per-launch API token and opens it in your browser (set `MCP_AUTO_OPEN_ENABLED=false` to stop it opening). See [Web client](/docs/draft/tools/inspector/web).
35The command prints a URL carrying a per-launch API token and opens it in your browser (set `MCP_AUTO_OPEN_ENABLED=false` to stop it opening). See [Web client](/docs/draft/tools/inspector/web.md).
3436
3537**CLI**
3638
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4345 --method tools/call --tool-name get_weather --tool-arg city=Boston --format json | jq .result
4446```
4547
46See [CLI client](/docs/draft/tools/inspector/cli).
48See [CLI client](/docs/draft/tools/inspector/cli.md).
4749
4850**TUI**
4951
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5153npx @modelcontextprotocol/inspector --tui node path/to/server/index.js
5254```
5355
54See [TUI client](/docs/draft/tools/inspector/tui).
56See [TUI client](/docs/draft/tools/inspector/tui.md).
5557
5658### Inspecting published servers
5759
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8587> sessions, Termux, and containers with a mounted volume) they are saved to
8688> `~/.mcp-inspector/secrets.json` instead, **unencrypted unless you supply a
8789> key**. See [Where secrets are
88> stored](/docs/draft/tools/inspector/configuration#where-secrets-are-stored)
90> stored](/docs/draft/tools/inspector/configuration.md#where-secrets-are-stored)
8991> for how to get a keychain back, encrypt the file, or keep secrets in memory
9092> only.
9193
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96981. **The mode flag:** `--web` (default), `--cli`, or `--tui`. At most one; passing two errors with `Specify at most one of --web, --cli, or --tui.`
97992. **`-h` / `--help`.**
98100
99Everything else (`--catalog`, `--config`, `--server-url`, `--transport`, `--method`, the OAuth flags) is defined by the *client*, not the launcher, and the clients do not all define the same set. The [Configuration and flags](/docs/draft/tools/inspector/configuration) page is organized that way, by owner.
101Everything else (`--catalog`, `--config`, `--server-url`, `--transport`, `--method`, the OAuth flags) is defined by the *client*, not the launcher, and the clients do not all define the same set. The [Configuration and flags](/docs/draft/tools/inspector/configuration.md) page is organized that way, by owner.
100102
101103> [!NOTE]
102104>
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115117
116118## Where to go next
117119
118> **[Web client](/docs/draft/tools/inspector/web)**
120> **[Web client](/docs/draft/tools/inspector/web.md)**
119121>
120122> A tab-by-tab walkthrough of the graphical inspector.
121123
122> **[CLI client](/docs/draft/tools/inspector/cli)**
124> **[CLI client](/docs/draft/tools/inspector/cli.md)**
123125>
124126> Method reference, output formats, exit codes, and CI recipes.
125127
126> **[TUI client](/docs/draft/tools/inspector/tui)**
128> **[TUI client](/docs/draft/tools/inspector/tui.md)**
127129>
128130> Terminal navigation and keyboard reference.
129131
130> **[Configuration and flags](/docs/draft/tools/inspector/configuration)**
132> **[Configuration and flags](/docs/draft/tools/inspector/configuration.md)**
131133>
132134> Catalog vs. config files, the full per-client flag reference, and
133135> environment variables.
134136
135> **[Authorization](/docs/draft/tools/inspector/authorization)**
137> **[Authorization](/docs/draft/tools/inspector/authorization.md)**
136138>
137139> The OAuth flow end to end, mid-session re-authorization, and loopback
138140> callbacks.
139141
140> **[Protocol eras](/docs/draft/tools/inspector/protocol-eras)**
142> **[Protocol eras](/docs/draft/tools/inspector/protocol-eras.md)**
141143>
142144> Legacy vs. modern (2026-07-28) operation, and how every tab changes between
143145> protocol eras.
144146
145> **[mcpdo connection client](/docs/draft/tools/inspector/mcpdo)**
147> **[mcpdo connection client](/docs/draft/tools/inspector/mcpdo.md)**
146148>
147149> Connect once, then run many commands against a named connection.
148150
149> **[Security](/docs/draft/tools/inspector/security)**
151> **[Security](/docs/draft/tools/inspector/security.md)**
150152>
151153> The threat model: the web backend's token, Docker, secret storage, stdio
152154> servers, and the mcpdo daemon.
153155
154> **[Recipes](/docs/draft/tools/inspector/recipes)**
156> **[Recipes](/docs/draft/tools/inspector/recipes.md)**
155157>
156158> Importing client configs, reviewing MCP Apps, Docker, and network hosting.
157159
158> **[Debugging guide](/docs/draft/tools/debugging)**
160> **[Debugging guide](/docs/draft/tools/debugging.md)**
159161>
160162> Broader debugging strategies beyond the Inspector.
161163
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