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

With no annotations provided, the description carries the full burden of behavioral disclosure, and it does well: it reveals a non-obvious side effect (warming the XCTest runner build cache in the background on iOS simulators), a hard constraint ('Times out after 90s'), and the nature of the output (compact evidence). Minor gaps remain, such as whether the tool opens sessions or performs network calls beyond 'server reachability,' but the critical behaviors are disclosed.

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?

Three sentences with zero filler: purpose and return shape in the first, the critical iOS cache-warming caveat and usage timing in the second, and the timeout in the third. Each sentence carries distinct, necessary information, and the primary purpose is front-loaded. For a 17-parameter tool, this is an exemplary length.

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?

The output schema exists, so return-value details are already covered outside the description. For a complex tool with no annotations, the description covers the essential workflow: what it diagnoses, what it returns, the iOS-specific prerequisite behavior, and the 90s timeout. It is slightly incomplete in not addressing how local-vs-remote (the remote parameter) or platform selection changes the diagnostic scope, but the core orientation is solid.

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?

Schema description coverage is 100%, so the baseline is 3 even without parameter details in the description itself. The description does not map its terms (e.g., 'server reachability', 'optional app discovery') to specific selectors like remote or targetApp, which would have added value. It adds no parameter-level meaning beyond the schema, so the baseline 3 is appropriate.

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 uses a specific verb (Diagnose) with an explicit resource scope: device, app, development-server, and React Native or Expo readiness issues. It also specifies what evidence is returned (local inventory, sessions, app discovery, toolchains, server reachability), making the purpose concrete. However, it does not explicitly differentiate from diagnostic siblings like devices, capabilities, network, or perf, which overlap in the diagnostic space.

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?

The description gives explicit, actionable timing guidance: 'run it before the first Apple snapshot or interaction of a session' in connection with the XCTest cache-warming behavior. It also implies the tool's diagnostic role in a session workflow. It names no alternatives or when-not-to-use conditions, so it stops short of a 5.

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