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

With no annotations provided, the description carries the behavioral disclosure burden. It discloses that no automation session is required, that sampling is over a short window, and that utilization metrics are returned only 'when available.' It does not describe potential side effects or permission needs, but for a read-only FPS sampler the essential behaviors are covered.

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

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

The description is two tight sentences with zero fluff. It front-loads the core purpose and output, then adds the key usage caveat and sibling reference. Every sentence earns its place, making it easy to parse quickly.

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

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

For a simple two-parameter tool with no output schema, the description covers everything an agent needs: what it does, what it returns, the device requirement, the session-free nature, and the crucial 'drive the app first' caveat. No critical information is missing for correct invocation.

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

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

The input schema has 100% description coverage for both parameters (udid and durationMs). The description adds little beyond what the schema already states—it mentions 'short window' but doesn't elaborate on durationMs specifics. Since schema covers parameters fully, a baseline of 3 is appropriate; the description adds no significant new meaning.

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

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

The description opens with a specific verb ('Sample'), resource ('on-device rendering FPS'), and target platform ('physical iOS device'), and explicitly states the returned metrics (mean/min/max FPS plus utilization). It also names the sibling tool 'android_fps' as the iOS counterpart, clearly distinguishing it from other performance tools.

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

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

It provides clear context on when to use: 'No automation session required' and notes that FPS reflects whatever is on screen, advising to 'drive the app first for a meaningful reading.' While it doesn't list explicit when-not-to-use scenarios or alternatives beyond android_fps, the guidance is actionable and sufficient for a sampling tool.

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