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

Annotations already declare readOnlyHint and destructiveHint, covering safety. The description adds the macOS-specific scope and optional group filter but does not disclose behaviors like default limit, ordering, or pagination. With annotations present, this is adequate but not exceptional.

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?

The description is two short sentences, front-loaded with the primary action and resource, followed by the optional filter. Every word earns its place; no filler or redundancy.

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 simple list tool with an output schema, both optional parameters documented, and safety annotations present, the description is nearly sufficient. The main gap is lack of usage differentiation from sibling tools, but that is largely covered by the purpose statement and tool name.

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 input schema fully documents both parameters with descriptions and defaults, so schema coverage is 100%. The description's mention of 'filter by group' adds no new semantic detail beyond what the schema's group_name description already provides.

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 clearly states the tool lists contacts from the macOS Contacts app, with an optional filter by group. It specifies both the resource (macOS Contacts) and the action (list), distinguishing it from siblings like m365_list_contacts and search_contacts.

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 description provides no explicit guidance on when to use this tool versus alternatives such as search_contacts or get_contact. While the 'macOS Contacts app' scoping implies local contacts, there is no direct comparison or exclusionary language.

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