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zoom_region

Zoom into a specific rectangle of the current screenshot and recapture it at native resolution for a sharp, legible magnified view. Use to read exact coordinates on surfaces without visible marks or to stay focused on one area.

Instructions

Zoom into a rectangle of the CURRENT image (the last screenshot's pixel space) and re-capture it at native resolution — a sharp, legible magnified view. Only that rectangle is captured (not the whole display), so it is also smaller and quicker to take than a full-display shot. Use it to read exact positions on surfaces that expose no marks (canvas/games, custom-rendered views) before clicking, or to stay scoped while working inside one area. Pass x, y, width, height in the current image's pixels (width,height > 0). The returned image becomes the new coordinate space, and clicks afterward map into the zoomed region automatically. marks defaults OFF (read coordinates off the overlaid grid); grid defaults ON. Take a screenshot first so there is an image to zoom into.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
xYesLeft edge of the rectangle, in the CURRENT image's pixel space (the last screenshot's coordinates).
yYesTop edge of the rectangle, in the current image's pixel space.
gridNoOverlay a labeled coordinate grid. Defaults ON for a zoom (coordinate mode); pass grid=false to suppress it.
marksNoSet-of-Mark numbering. Defaults OFF for a zoom — the zoom is the tool for surfaces that expose no marks, so you read coordinates off the grid. Pass marks=true to also number any actionable elements inside the region.
widthYesWidth of the rectangle in current-image pixels. Must be > 0.
heightYesHeight of the rectangle in current-image pixels. Must be > 0.
Behavior5/5

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

With no annotations, the description fully explains behavior: re-captures only the rectangle (smaller and quicker), the image becomes the new coordinate space, clicks map automatically, and defaults for marks (OFF) and grid (ON) are stated. No contradictions.

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?

Every sentence is informative: purpose, benefits, use cases, parameter details, coordinate mapping, defaults. No redundancy. Well-structured with front-loaded key information.

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

Completeness5/5

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

Despite no output schema, the description explains the outcome (new image as coordinate space) and side effects. Covers all 6 parameters' roles, defaults, and constraints. Complete for a tool with coordinate transformation complexity.

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

Parameters5/5

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

Schema coverage is 100%, but the description adds context: explains pixel space coordinates, rectangle constraints (width, height > 0), defaults for grid and marks, and the coordinate transformation effect. This adds significant meaning beyond schema property descriptions.

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 zooms into a rectangle of the current image and re-captures it at native resolution, distinguishing it from full-display screenshot tools. The verb 'zoom' and resource 'rectangle of the current image' are specific, and the description contrasts with a full-display shot.

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

Usage Guidelines5/5

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

Explicitly states when to use: to read exact positions on surfaces with no marks (canvas/games, custom-rendered views) or to stay scoped in one area. Implicitly advises against using when marks are available, and describes the coordinate remapping effect for subsequent clicks.

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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