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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, closed-world, so the safety profile is covered. The description adds that each insight carries a ready-to-send draft message, which is useful behavioral context. It adds nothing about permissions, rate limits, or ordering beyond that.

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 compact sentences that front-load the usage trigger before the content examples. The example list is slightly long but each example earns its place by illustrating a distinct insight type.

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 an output schema present, the description needn't explain return shape, and rich annotations cover safety. The description supplies the missing piece – what kinds of insights and the draft-message payload – making it adequately complete for a one-parameter, zero-required list tool.

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?

There is a single optional 'limit' parameter with 100% schema description coverage, so the schema fully documents it (default 5, max 10). The description contributes nothing about the limit or how results are ordered/selected. Baseline 3 is appropriate when the schema does all the work.

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, together with the title, makes clear the tool surfaces surprising relationship insights, and the concrete examples (birthday plus long silence, fading friendship, new contact) distinguish it from generic list siblings like contacts.timeline.list. However, the body never states an explicit verb+resource ('returns a list of insights') – the purpose is conveyed through scenario framing rather than a direct statement.

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 gives an explicit trigger: 'When the user wants something impressive or delightful about their relationships.' That is a clear condition for invocation. There are no exclusions or named alternatives, 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.