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trace

Start or stop trace capture for debugging apps on iOS, Android, desktop, and TV devices. Specify action, device, and session to control tracing.

Instructions

Start or stop trace capture.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
cwdNoWorking directory for command execution.
pathNo
udidNoiOS device UDID selector.
debugNoEnable debug diagnostics.
runIdNoLease run identifier.
actionYes
deviceNoDevice name selector.
serialNoAndroid serial selector.
targetNoAlias for deviceTarget on commands without a UI target field. Interaction commands reserve target for the UI element.
tenantNoRemote tenant identifier.
leaseIdNoExisting lease identifier.
sessionNoAgent-device session name.
platformNoPlatform selector used to resolve a device.
stateDirNoAgent-device state directory.
includeCostNoInclude per-command agent-cost (cost.wallClockMs, …) in structuredContent. Defaults to off; the default response shape is unchanged.
deviceTargetNoDevice target form. Maps to the CLI --target flag.
daemonBaseUrlNoRemote daemon base URL.
responseLevelNoResponse verbosity: token-cheap digest / default (today) / full. Defaults to default; the default response shape is unchanged.
daemonAuthTokenNoRemote daemon auth token.
iosXctestEnvDirNoWritable directory for iOS XCTest runner env overlays.
mcpOutputFormatNoMCP text content format. Defaults to optimized agent-friendly text; use json for JSON text. Structured content is always returned separately.
iosXctestrunFileNoExternally built iOS XCTest runner .xctestrun artifact path.
iosSimulatorDeviceSetNoiOS simulator device-set path used for device resolution.
androidDeviceAllowlistNoAndroid serial allowlist used for device resolution.
iosXctestDerivedDataPathNoDerived data path for external iOS XCTest runner execution.
Behavior2/5

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

With no annotations, the brief description fails to disclose behavioral traits such as side effects, data collection impact, or what happens on start/stop. Agents cannot infer the operational consequences.

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 a single sentence, concise and front-loaded. However, it is so brief that it sacrifices necessary detail, slightly reducing effectiveness.

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

Completeness2/5

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

The tool has 25 parameters and no output schema. The description does not explain the purpose of trace capture, return values, or how to interpret results, leaving the agent underinformed.

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 coverage is 92%, so the baseline is 3. The description adds no additional meaning beyond the schema, which already documents the 'action' parameter as start/stop.

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 'Start or stop trace capture' clearly states the verb and resource. It is unambiguous but lacks specificity about what kind of trace (e.g., network, performance), which could improve clarity further.

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?

No guidance is provided on when to use this tool versus siblings like 'record' or 'replay'. The description does not mention context, prerequisites, or alternatives.

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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