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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=false), and the description adds context those annotations cannot convey: it stores only the latest location (overwrite semantics), it returns nearby contacts with known addresses, and it makes a privacy guarantee that contacts are never tracked. That is meaningful behavioral disclosure beyond the structured fields.

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 sentences of reasonable length, but the opening is an awkward fragment – a when-clause terminated as if it were a full sentence – which delays the actual purpose. The most useful information (storage and return behavior) is not front-loaded, so structure is adequate but not clean.

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?

An output schema exists so return values need no further explanation, and annotations carry the safety profile. The description still supplies the usage trigger, storage behavior, and privacy constraint, leaving little an agent needs before calling 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% (latitude, longitude, accuracy_meters all documented), so the schema already carries parameter meaning. The description adds no syntax, format, or range detail beyond it, so the baseline of 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?

The description states a specific effect – 'Stores only the latest location and returns contacts with known addresses nearby' – which tells an agent what the tool accomplishes. However, it leads with a usage-trigger clause rather than the purpose, and it does not distinguish itself from siblings like proximity.checkin or proximity.contacts.list. Clear enough to identify the operation, but not sharply differentiated.

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 sentence gives an explicit trigger: 'When the user shares their current location, or you have it from context and they would want nearby people surfaced.' That is a clear when-to-use condition. It stops short of naming alternatives (e.g. proximity.checkin) or stating when not to use it, so it falls below a 5.

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