Contacts Unresolved

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

The description is consistent with readOnlyHint=true and openWorldHint=false, and it adds the selection behavior (filtering handles that fail to resolve to a contact). It does not add much beyond the annotations and the basic purpose, such as aggregation rules, pagination, or ordering, though an output schema exists.

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?

A single, front-loaded sentence states exactly what is returned and under what condition. Every word contributes, with no repetition of the title or redundant 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?

Given the tool's simplicity, one optional well-documented parameter, read-only annotations, and an output schema, the description covers the core behavior needed to invoke it. It is complete enough for a straightforward list operation, though an explicit note on when to prefer it over contact-search siblings would round it out.

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 only parameter, min_messages, has 100% schema description coverage ('Minimum message count to include (default 5)'), so the description does not need to repeat it. The tool description adds no supplementary context about how the threshold interacts with the unresolved-handle list, leaving the schema to carry the semantics.

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 names a specific verb ('List') and resource ('iMessage handles') with a precise inclusion criterion ('don't resolve to any contact name'). This clearly differentiates it from sibling tools like contacts_search and contacts_get, which operate on known contact records.

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 intended use is implied by the definition: an agent should call this when it needs iMessage handles that have no matching contact. However, it never explicitly contrasts this with contacts_search or contacts_get, nor states when not to use it, so the guidance is inferred rather than stated.

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