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

Annotations already declare this a safe, idempotent, read-only, closed-world read, so the safety profile is covered. The description adds genuine behavioral context beyond that: it discloses the returned fields and, more importantly, a presentation directive ('Present gently, never as alerts') that shapes how the agent should surface the output. It stops short of noting freshness, location prerequisites, or rate limits for a proximity-dependent read.

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 with zero filler. The trigger condition is front-loaded, followed by output contents and then presentation guidance in priority order. Every sentence carries distinct information.

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 is not obliged to detail return values, yet it usefully summarizes them. Combined with the usage trigger and presentation instruction, an agent has enough to call and relay the tool. Minor gaps remain around environmental prerequisites implied by 'nearby,' but nothing essential 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?

The tool takes zero parameters, so the schema baseline of 4 applies and there is nothing for the description to disambiguate. No parameter-level meaning is needed or missing.

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?

States a specific verb and resource: it returns a discrete heads-up about people physically nearby, itemizing the fields (name, distance, last contact, birthday, open tasks, note suggestion). The scope is clear, but it never explicitly distinguishes itself from adjacent siblings like proximity.contacts.list or agent.briefing.get, leaving the agent to infer which to call. A clear purpose, but not fully disambiguated from its family.

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 opening clause is an explicit when-to-use trigger: 'When the user is out and wants a discreet heads-up about the people around them right now.' That is a real situational gate. However, it names no alternatives and gives no when-not-to-use guidance (e.g., why not proximity.contacts.list), so the routing signal is present but incomplete.

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