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Merge pull request modelcontextprotocol#177 from nbarraud/cli-and-config-file-support
Add CLI and config file support
2 parents 5fa76a7 + fd7dbba commit f7272d8

23 files changed

+6727
-2973
lines changed

‎.gitignore

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Original file line numberDiff line numberDiff line change
@@ -1,7 +1,11 @@
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.DS_Store
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node_modules
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node_modules/
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*-workspace/
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server/build
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client/dist
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client/tsconfig.app.tsbuildinfo
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client/tsconfig.node.tsbuildinfo
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.vscode
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bin/build
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cli/build
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test-output

‎README.md

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@@ -21,13 +21,13 @@ You can pass both arguments and environment variables to your MCP server. Argume
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npx @modelcontextprotocol/inspector build/index.js arg1 arg2
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# Pass environment variables only
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npx @modelcontextprotocol/inspector -e KEY=value -e KEY2=$VALUE2 node build/index.js
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npx @modelcontextprotocol/inspector -e key=value -e key2=$VALUE2 node build/index.js
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# Pass both environment variables and arguments
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npx @modelcontextprotocol/inspector -e KEY=value -e KEY2=$VALUE2 node build/index.js arg1 arg2
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npx @modelcontextprotocol/inspector -e key=value -e key2=$VALUE2 node build/index.js arg1 arg2
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# Use -- to separate inspector flags from server arguments
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npx @modelcontextprotocol/inspector -e KEY=$VALUE -- node build/index.js -e server-flag
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npx @modelcontextprotocol/inspector -e key=$VALUE -- node build/index.js -e server-flag
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```
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The inspector runs both an MCP Inspector (MCPI) client UI (default port 6274) and an MCP Proxy (MCPP) server (default port 6277). Open the MCPI client UI in your browser to use the inspector. (These ports are derived from the T9 dialpad mapping of MCPI and MCPP respectively, as a mnemonic). You can customize the ports if needed:
@@ -59,6 +59,36 @@ The MCP Inspector supports the following configuration settings. To change them,
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These settings can be adjusted in real-time through the UI and will persist across sessions.
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The inspector also supports configuration files to store settings for different MCP servers. This is useful when working with multiple servers or complex configurations:
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```bash
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npx @modelcontextprotocol/inspector --config path/to/config.json --server everything
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```
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Example server configuration file:
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```json
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{
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"mcpServers": {
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"everything": {
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"command": "npx",
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"args": ["@modelcontextprotocol/server-everything"],
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"env": {
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"hello": "Hello MCP!"
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}
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},
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"my-server": {
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"command": "node",
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"args": ["build/index.js", "arg1", "arg2"],
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"env": {
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"key": "value",
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"key2": "value2"
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}
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}
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}
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}
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```
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### From this repository
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If you're working on the inspector itself:
@@ -83,6 +113,57 @@ npm run build
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npm start
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```
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### CLI Mode
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CLI mode enables programmatic interaction with MCP servers from the command line, ideal for scripting, automation, and integration with coding assistants. This creates an efficient feedback loop for MCP server development.
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```bash
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npx @modelcontextprotocol/inspector --cli node build/index.js
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```
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The CLI mode supports most operations across tools, resources, and prompts. A few examples:
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```bash
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# Basic usage
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npx @modelcontextprotocol/inspector --cli node build/index.js
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# With config file
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npx @modelcontextprotocol/inspector --cli --config path/to/config.json --server myserver
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# List available tools
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npx @modelcontextprotocol/inspector --cli node build/index.js --method tools/list
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# Call a specific tool
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npx @modelcontextprotocol/inspector --cli node build/index.js --method tools/call --tool-name mytool --tool-arg key=value --tool-arg another=value2
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# List available resources
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npx @modelcontextprotocol/inspector --cli node build/index.js --method resources/list
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# List available prompts
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npx @modelcontextprotocol/inspector --cli node build/index.js --method prompts/list
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# Connect to a remote MCP server
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npx @modelcontextprotocol/inspector --cli https://my-mcp-server.example.com
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# Call a tool on a remote server
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npx @modelcontextprotocol/inspector --cli https://my-mcp-server.example.com --method tools/call --tool-name remotetool --tool-arg param=value
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# List resources from a remote server
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npx @modelcontextprotocol/inspector --cli https://my-mcp-server.example.com --method resources/list
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```
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### UI Mode vs CLI Mode: When to Use Each
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| Use Case | UI Mode | CLI Mode |
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| ------------------------ | ------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
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| **Server Development** | Visual interface for interactive testing and debugging during development | Scriptable commands for quick testing and continuous integration; creates feedback loops with AI coding assistants like Cursor for rapid development |
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| **Resource Exploration** | Interactive browser with hierarchical navigation and JSON visualization | Programmatic listing and reading for automation and scripting |
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| **Tool Testing** | Form-based parameter input with real-time response visualization | Command-line tool execution with JSON output for scripting |
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| **Prompt Engineering** | Interactive sampling with streaming responses and visual comparison | Batch processing of prompts with machine-readable output |
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| **Debugging** | Request history, visualized errors, and real-time notifications | Direct JSON output for log analysis and integration with other tools |
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| **Automation** | N/A | Ideal for CI/CD pipelines, batch processing, and integration with coding assistants |
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| **Learning MCP** | Rich visual interface helps new users understand server capabilities | Simplified commands for focused learning of specific endpoints |
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## License
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This project is licensed under the MIT License—see the [LICENSE](LICENSE) file for details.

‎bin/cli.js

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@@ -1,57 +1,34 @@
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#!/usr/bin/env node
2-
3-
import { resolve, dirname } from "path";
2+
import { Command } from "commander";
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import fs from "node:fs";
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import path from "node:path";
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import { dirname, resolve } from "path";
46
import { spawnPromise } from "spawn-rx";
57
import { fileURLToPath } from "url";
6-
78
const __dirname = dirname(fileURLToPath(import.meta.url));
8-
9+
function handleError(error) {
10+
let message;
11+
if (error instanceof Error) {
12+
message = error.message;
13+
} else if (typeof error === "string") {
14+
message = error;
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} else {
16+
message = "Unknown error";
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}
18+
console.error(message);
19+
process.exit(1);
20+
}
921
function delay(ms) {
1022
return new Promise((resolve) => setTimeout(resolve, ms, true));
1123
}
12-
13-
async function main() {
14-
// Parse command line arguments
15-
const args = process.argv.slice(2);
16-
const envVars = {};
17-
const mcpServerArgs = [];
18-
let command = null;
19-
let parsingFlags = true;
20-
21-
for (let i = 0; i < args.length; i++) {
22-
const arg = args[i];
23-
24-
if (parsingFlags && arg === "--") {
25-
parsingFlags = false;
26-
continue;
27-
}
28-
29-
if (parsingFlags && arg === "-e" && i + 1 < args.length) {
30-
const envVar = args[++i];
31-
const equalsIndex = envVar.indexOf("=");
32-
33-
if (equalsIndex !== -1) {
34-
const key = envVar.substring(0, equalsIndex);
35-
const value = envVar.substring(equalsIndex + 1);
36-
envVars[key] = value;
37-
} else {
38-
envVars[envVar] = "";
39-
}
40-
} else if (!command) {
41-
command = arg;
42-
} else {
43-
mcpServerArgs.push(arg);
44-
}
45-
}
46-
24+
async function runWebClient(args) {
4725
const inspectorServerPath = resolve(
4826
__dirname,
4927
"..",
5028
"server",
5129
"build",
5230
"index.js",
5331
);
54-
5532
// Path to the client entry point
5633
const inspectorClientPath = resolve(
5734
__dirname,
@@ -60,43 +37,38 @@ async function main() {
6037
"bin",
6138
"cli.js",
6239
);
63-
6440
const CLIENT_PORT = process.env.CLIENT_PORT ?? "6274";
6541
const SERVER_PORT = process.env.SERVER_PORT ?? "6277";
66-
6742
console.log("Starting MCP inspector...");
68-
6943
const abort = new AbortController();
70-
7144
let cancelled = false;
7245
process.on("SIGINT", () => {
7346
cancelled = true;
7447
abort.abort();
7548
});
76-
let server, serverOk;
49+
let server;
50+
let serverOk;
7751
try {
7852
server = spawnPromise(
7953
"node",
8054
[
8155
inspectorServerPath,
82-
...(command ? [`--env`, command] : []),
83-
...(mcpServerArgs ? [`--args=${mcpServerArgs.join(" ")}`] : []),
56+
...(args.command ? [`--env`, args.command] : []),
57+
...(args.args ? [`--args=${args.args.join(" ")}`] : []),
8458
],
8559
{
8660
env: {
8761
...process.env,
8862
PORT: SERVER_PORT,
89-
MCP_ENV_VARS: JSON.stringify(envVars),
63+
MCP_ENV_VARS: JSON.stringify(args.envArgs),
9064
},
9165
signal: abort.signal,
9266
echoOutput: true,
9367
},
9468
);
95-
9669
// Make sure server started before starting client
9770
serverOk = await Promise.race([server, delay(2 * 1000)]);
9871
} catch (error) {}
99-
10072
if (serverOk) {
10173
try {
10274
await spawnPromise("node", [inspectorClientPath], {
@@ -108,13 +80,138 @@ async function main() {
10880
if (!cancelled || process.env.DEBUG) throw e;
10981
}
11082
}
111-
112-
return 0;
11383
}
114-
115-
main()
116-
.then((_) => process.exit(0))
117-
.catch((e) => {
118-
console.error(e);
119-
process.exit(1);
84+
async function runCli(args) {
85+
const projectRoot = resolve(__dirname, "..");
86+
const cliPath = resolve(projectRoot, "cli", "build", "index.js");
87+
const abort = new AbortController();
88+
let cancelled = false;
89+
process.on("SIGINT", () => {
90+
cancelled = true;
91+
abort.abort();
12092
});
93+
try {
94+
await spawnPromise("node", [cliPath, args.command, ...args.args], {
95+
env: { ...process.env, ...args.envArgs },
96+
signal: abort.signal,
97+
echoOutput: true,
98+
});
99+
} catch (e) {
100+
if (!cancelled || process.env.DEBUG) {
101+
throw e;
102+
}
103+
}
104+
}
105+
function loadConfigFile(configPath, serverName) {
106+
try {
107+
const resolvedConfigPath = path.isAbsolute(configPath)
108+
? configPath
109+
: path.resolve(process.cwd(), configPath);
110+
if (!fs.existsSync(resolvedConfigPath)) {
111+
throw new Error(`Config file not found: ${resolvedConfigPath}`);
112+
}
113+
const configContent = fs.readFileSync(resolvedConfigPath, "utf8");
114+
const parsedConfig = JSON.parse(configContent);
115+
if (!parsedConfig.mcpServers || !parsedConfig.mcpServers[serverName]) {
116+
const availableServers = Object.keys(parsedConfig.mcpServers || {}).join(
117+
", ",
118+
);
119+
throw new Error(
120+
`Server '${serverName}' not found in config file. Available servers: ${availableServers}`,
121+
);
122+
}
123+
const serverConfig = parsedConfig.mcpServers[serverName];
124+
return serverConfig;
125+
} catch (err) {
126+
if (err instanceof SyntaxError) {
127+
throw new Error(`Invalid JSON in config file: ${err.message}`);
128+
}
129+
throw err;
130+
}
131+
}
132+
function parseKeyValuePair(value, previous = {}) {
133+
const parts = value.split("=");
134+
const key = parts[0];
135+
const val = parts.slice(1).join("=");
136+
if (val === undefined || val === "") {
137+
throw new Error(
138+
`Invalid parameter format: ${value}. Use key=value format.`,
139+
);
140+
}
141+
return { ...previous, [key]: val };
142+
}
143+
function parseArgs() {
144+
const program = new Command();
145+
const argSeparatorIndex = process.argv.indexOf("--");
146+
let preArgs = process.argv;
147+
let postArgs = [];
148+
if (argSeparatorIndex !== -1) {
149+
preArgs = process.argv.slice(0, argSeparatorIndex);
150+
postArgs = process.argv.slice(argSeparatorIndex + 1);
151+
}
152+
program
153+
.name("inspector-bin")
154+
.allowExcessArguments()
155+
.allowUnknownOption()
156+
.option(
157+
"-e <env>",
158+
"environment variables in KEY=VALUE format",
159+
parseKeyValuePair,
160+
{},
161+
)
162+
.option("--config <path>", "config file path")
163+
.option("--server <n>", "server name from config file")
164+
.option("--cli", "enable CLI mode");
165+
// Parse only the arguments before --
166+
program.parse(preArgs);
167+
const options = program.opts();
168+
const remainingArgs = program.args;
169+
// Add back any arguments that came after --
170+
const finalArgs = [...remainingArgs, ...postArgs];
171+
// Validate that config and server are provided together
172+
if (
173+
(options.config && !options.server) ||
174+
(!options.config && options.server)
175+
) {
176+
throw new Error(
177+
"Both --config and --server must be provided together. If you specify one, you must specify the other.",
178+
);
179+
}
180+
// If config file is specified, load and use the options from the file. We must merge the args
181+
// from the command line and the file together, or we will miss the method options (--method,
182+
// etc.)
183+
if (options.config && options.server) {
184+
const config = loadConfigFile(options.config, options.server);
185+
return {
186+
command: config.command,
187+
args: [...(config.args || []), ...finalArgs],
188+
envArgs: { ...(config.env || {}), ...(options.e || {}) },
189+
cli: options.cli || false,
190+
};
191+
}
192+
// Otherwise use command line arguments
193+
const command = finalArgs[0] || "";
194+
const args = finalArgs.slice(1);
195+
return {
196+
command,
197+
args,
198+
envArgs: options.e || {},
199+
cli: options.cli || false,
200+
};
201+
}
202+
async function main() {
203+
process.on("uncaughtException", (error) => {
204+
handleError(error);
205+
});
206+
try {
207+
const args = parseArgs();
208+
if (args.cli) {
209+
runCli(args);
210+
} else {
211+
await runWebClient(args);
212+
}
213+
} catch (error) {
214+
handleError(error);
215+
}
216+
}
217+
main();

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