Dittu

set_corners

Update the phone's screen-corner calibration.
Each corner is [nx, ny] normalized 0.0–1.0 in the raw camera frame.
tl/tr/br/bl = top-left/top-right/bottom-right/bottom-left of the monitor as seen
by the camera (an arbitrary trapezoid due to perspective — not a rectangle).
Call get_corners() first to read the current values before nudging one of them.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "tl": "<tl>",
      "tr": "<tr>",
      "br": "<br>",
      "bl": "<bl>"
    },
    "name": "set_corners"
  }
}

Input Schema

Name	Required	Description	Default
`bl`	Yes
`br`	Yes
`tl`	Yes
`tr`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 9, 2026

TDQS

A4.2/5.0

Behavior3/5

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

With no annotations, the description explains the coordinate system and perspective trapezoid, but does not specify persistence, permissions, or side effects of calibration updates. Some transparency but incomplete.

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?

Three sentences: purpose, coordinate definition, usage advice. No redundant words, front-loaded with primary action.

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

Completeness4/5

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

Covers parameters, coordinate system, and prerequisite. Output schema exists so return values not needed. Missing potential details like range validation or effect scope, but sufficient for typical use.

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

Parameters4/5

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

Schema has 0% parameter description coverage. Description compensates by explaining each corner's role and that each is a normalized [nx, ny] array in camera frame, adding significant meaning beyond schema.

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

Purpose5/5

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

The description clearly states the tool updates screen-corner calibration, defines the normalized coordinate system, and differentiates from sibling get_corners by recommending calling it first to read current values.

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

Usage Guidelines4/5

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

Explicitly advises calling get_corners() first before modifying, establishing a clear usage pattern. Does not mention when not to use or alternatives, but provides necessary context.

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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