Mobile Next MCP

Save Screenshot

mobile_save_screenshot

Destructive

Capture and save screenshots from mobile devices for automation testing and debugging purposes. Specify device identifier and file path to store the image.

Instructions

Save a screenshot of the mobile device to a file

Input Schema

TableJSON Schema

Name	Required	Description	Default
`device`	Yes	The device identifier to use. Use mobile_list_available_devices to find which devices are available to you.
`saveTo`	Yes	The path to save the screenshot to

Implementation Reference

src/server.ts:384-397 (registration)

Registration of the 'mobile_save_screenshot' tool, including input schema (saveTo path) and inline handler that uses the selected robot to capture and save a screenshot to the specified file path.

tool(
	"mobile_save_screenshot",
	"Save a screenshot of the mobile device to a file",
	{
		saveTo: z.string().describe("The path to save the screenshot to"),
	},
	async ({ saveTo }) => {
		requireRobot();

		const screenshot = await robot!.getScreenshot();
		fs.writeFileSync(saveTo, screenshot);
		return `Screenshot saved to: ${saveTo}`;
	}
);

src/server.ts:384-397 (handler)

The handler function for 'mobile_save_screenshot' is defined inline during registration. It requires a selected robot/device, captures the screenshot buffer via robot.getScreenshot(), and writes it synchronously to the filesystem using fs.writeFileSync.

tool(
	"mobile_save_screenshot",
	"Save a screenshot of the mobile device to a file",
	{
		saveTo: z.string().describe("The path to save the screenshot to"),
	},
	async ({ saveTo }) => {
		requireRobot();

		const screenshot = await robot!.getScreenshot();
		fs.writeFileSync(saveTo, screenshot);
		return `Screenshot saved to: ${saveTo}`;
	}
);

src/server.ts:388-388 (schema)
Input schema for 'mobile_save_screenshot' tool: requires a 'saveTo' string parameter specifying the file path.
```
saveTo: z.string().describe("The path to save the screenshot to"),
```

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv1.0.0Jan 3, 2026

removedInput schema / additionalProperties
```
Removed value: -false
```

addedInput schema / properties / device

Added value: +{
+  "description": "The device identifier to use. Use mobile_list_available_devices to find which devices are available to you.",
+  "type": "string"
+}

changedInput schema / required

Previous value: -[
-  "saveTo"
-]New value: +[
+  "device",
+  "saveTo"
+]

First observedAug 15, 2025

TDQS

B3.3/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations include 'destructiveHint: true', indicating potential side effects like file system changes. The description adds value by specifying that it saves to a file, which clarifies the destructive nature. However, it lacks details on permissions, error handling, or rate limits, leaving behavioral gaps despite the annotation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, clear sentence with no wasted words. It's front-loaded with the core action and resource, making it easy to parse quickly. Every part of the sentence contributes directly to understanding the tool's function.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the destructive annotation and lack of output schema, the description adequately covers the basic action but misses details like return values or error conditions. It's sufficient for a simple tool but could benefit from more context about what happens after saving (e.g., success confirmation).

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 100% schema description coverage, the input schema fully documents both parameters ('device' and 'saveTo'). The description adds no additional semantic context beyond what's in the schema, such as file format or device compatibility details, so it meets the baseline but doesn't enhance understanding.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Save a screenshot') and resource ('of the mobile device to a file'), making the purpose immediately understandable. However, it doesn't differentiate from the sibling tool 'mobile_take_screenshot', which likely serves a similar function, leaving some ambiguity about when to use one versus the other.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives like 'mobile_take_screenshot'. It mentions the device parameter's dependency on 'mobile_list_available_devices', but this is part of the input schema, not explicit usage instructions. There's no mention of prerequisites, timing, or contextual factors.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.