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

With no annotations, the description carries the full burden. It goes beyond a simple operation statement by disclosing the error return 'no HID available' on iOS 17.x/no-tunnel, and clarifies the coordinate system. It does not mention success return values or the precondition that a contact must be held, but it is reasonably transparent for a low-risk HID action.

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 three sentences, front-loaded with the primary action, and every sentence adds value: the action, the pairing sibling, coordinate clarification, and the known failure condition. No wasteful filler.

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 lift operation with no output schema, the description covers the action, the coordinate system, the pairing relationship, and a specific error case. It lacks an explicit statement about what a successful return looks like and does not state the precondition that a contact must already be held, but these are minor gaps given the tool's simplicity.

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 coverage is 100%, so the baseline is 3. The description says 'Coordinates are iOS screen points', but the schema already explains this for x and y, including the norm parameter. No additional parameter-level semantics are provided beyond what the schema already contains.

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 starts with a specific verb and resource: 'Lift the held contact at (x,y) via direct HID input'. It clearly distinguishes this from siblings by noting it pairs with ios_contact_hid and states the action as mouse-button-up/touch-up.

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 by saying 'Pairs with ios_contact_hid' and notes 'no automation session needed' to differentiate from session-based alternatives. It also mentions the failure mode on iOS 17.x/no-tunnel, but does not explicitly list when not to use this tool or alternative tools beyond the pairing hint.

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