mobilerun-mcp

Scroll Down

scroll_down

Move the viewport down on a mobile screen to reveal hidden content, either by a centered swipe or within a specific scrollable element.

Instructions

Scroll the content down (reveal what is below): a centered swipe over half the screen (amount), or inside a scrollable mark (som_id).

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "scroll_down"
  }
}

Input Schema

Name	Required	Description	Default
`amount`	No
`device`	No
`som_id`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 27, 2026

TDQS

B3.4/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It does add real mechanism detail beyond the name — the gesture is a centered swipe over half the screen — which is genuinely useful. However it never states what happens at the end of content, whether the scroll is animated/instant, or any side effects on UI state, so it is only partially transparent for a UI-mutating action.

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

Conciseness4/5

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

A single front-loaded sentence that leads with the action and then qualifies it. Very little waste, though the parenthetical placement of '(amount)' and '(som_id)' makes the parameter mapping slightly choppy to read.

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?

An output schema exists, so return values needn't be explained. Still, with no annotations, 0% schema description coverage, and an undocumented 'device' parameter, the definition leaves gaps an agent must guess at — notably target-device handling and end-of-content behavior.

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?

Schema description coverage is 0%, so the description must compensate, and it partly does: it maps 'amount' to a fractional screen swipe and 'som_id' to a scrollable mark target. The third parameter (device) is never mentioned, and the amount's numeric scale/units are only vaguely implied by 'half the screen'.

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?

States a specific verb+resource ('Scroll the content down') with an operational gloss ('reveal what is below') and names the two execution modes (centered swipe via amount, in-place scroll via som_id). The direction word 'down' implicitly separates it from scroll_up/left/right siblings, though it never names them.

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

Usage Guidelines3/5

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

The description distinguishes the two calling modes (amount vs som_id), which is useful selection guidance internal to the tool, but it gives no when-to-use guidance relative to the many scrolling siblings (swipe, scroll, scroll_up, scroll_to, scroll_until, scroll_until). Nothing says when this is preferable to raw swipe or to scroll_to.

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

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