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tap_with_fallback

Sends a raw coordinate tap using native backend with Maestro fallback for WKWebView overlays where visual position differs from DOM hit-test. Verifies tap success via accessibility tree changes or screenshot delta.

Instructions

Sends a raw coordinate tap via the native backend (idb if installed, else a Maestro tapOn-point fallback). Useful for WKWebView game overlays where visual position differs from the DOM hit-test position. The Maestro fallback needs an app context: pass bundleId, or the foreground app is auto-detected. VERIFICATION: 'ok' is decided primarily by a change in the native accessibility element set before/after the tap (stable under animation/video). When no native backend is present it falls back to a screenshot byte-size delta (weak — animation can flip it). The result's oracle field reports which was used ('a11y-change' | 'screenshot-bytesize' | 'unverified'). For WebView-rendered targets the a11y tree won't change → oracle:'unverified'; confirm via webview_inspect. offsetStep defaults to 0 (tap the exact point); set it >0 only to deliberately probe nearby y-offsets on retry.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
udidYesSimulator / device UDID
xYesX coordinate in logical points
yYesY coordinate in logical points
bundleIdNoApp bundle id for the Maestro fallback (ignored when idb is present). Auto-detected if omitted.
maxRetriesNoMaximum tap attempts (default 3)
offsetStepNoOpt-in Y offset step in px applied per retry (default 0 = always tap the exact point; no blind walk).
Behavior5/5

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

With no annotations provided, the description fully carries the burden. It details fallback behavior, verification mechanisms, oracle field, conditions for each oracle type, and offsetStep behavior. Very transparent about potential issues like animation affecting screenshot verification.

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?

The description is dense with information but every sentence adds value. It is front-loaded with the main purpose and fallback. Slightly long but justified by complexity.

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?

Given the complexity (fallback, verification, oracle) and no output schema, the description covers return value ('oracle' field) and all crucial aspects. It is complete for the tool's purpose.

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 coverage is 100% (baseline 3). Description adds significant value beyond schema: explains bundleId auto-detection, offsetStep default behavior (no blind walk), maxRetries default, and verification context for each parameter.

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 it sends a raw coordinate tap via native backend with fallback, specifies use for WKWebView game overlays where visual position differs from DOM hit-test, and distinguishes from sibling tools like 'tap_on'.

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?

Provides explicit context for when to use (WKWebView overlays) and mentions verification details. Lacks explicit 'when not to use' but points to alternative 'webview_inspect' for WebView targets.

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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