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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the burden is low. The description adds real behavioral value by naming the output fields and their semantics (paused/mocked/aborted/passedThrough/errors) and the 'mocked: 0' interpretation, which no structured field provides.

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?

Two dense sentences, front-loaded with the core purpose and followed by the actionable diagnostic tip. Every clause earns its place with no redundancy.

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?

With no output schema, the description carries the return-value burden and does so by listing the reported state, target, routes, and counter fields. For a single-parameter read-only status tool, nothing needed to call it correctly is missing.

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% for the single udid parameter, so the schema already documents it fully. The description adds no additional parameter meaning, making the baseline 3 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?

Specific verb+resource: 'Report whether Safari/WKWebView interception is currently armed,' then enumerates exactly what is reported (target, active routes, counters). This cleanly distinguishes it from ios_safari_mock_add/clear/list/remove siblings, which change state rather than report it.

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?

Gives clear diagnostic context ('check the counters to confirm a mock is actually firing — a route that never matches shows mocked: 0'), which tells the agent when this tool is useful. It stops short of naming alternatives (e.g., ios_safari_mock_list) or stating exclusions.

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