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

Goes well beyond the annotations (which only say non-readonly, idempotent, non-destructive) by disclosing the atomic one-frame lift requirement and the reason releasing one at a time breaks the gesture, plus the concrete failure mode 'no HID available' on iOS 17.x/no-tunnel. This is real behavioral context an agent needs.

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 tight sentences, front-loaded with purpose, then the non-obvious behavioral constraint, then coordinate meaning and error case. Every sentence earns its place with no 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 mutation HID tool with no output schema, the description supplies the critical atomicity constraint, coordinate interpretation, and the documented failure return. Combined with full schema coverage and annotations, an agent has everything needed to call it correctly.

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 udid, points, ordering, and norm semantics are already documented in the schema. The description's 'Coordinates are where each finger ends' largely restates the schema's 'Where each finger is when it lifts', adding no new parameter meaning; baseline 3 applies.

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 ('Lift held contacts') that explicitly names its counterpart tool ios_contacts_hid, so an agent can distinguish release from placement without opening a schema. The scope (contacts placed by that sibling) is unambiguous.

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?

Implicitly establishes when to use it by anchoring to ios_contacts_hid ('contacts placed by ios_contacts_hid'), giving clear operational context. It does not state explicit exclusions or name alternative release tools such as ios_release_hid, 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.