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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the read-only nature is structurally disclosed. The description adds the data source and searchable fields, but it does not disclose additional behavioral traits such as permissions, rate limits, or limitations beyond what the annotations and schema already convey.

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 sentences, front-loaded with the core action and scope. The second sentence directs to alternatives without any unnecessary words or repetition.

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 simple read-only search tool with an output schema, strong annotations, and full schema parameter descriptions, the description covers the essential information: the source, searchable fields, and alternative tools. An agent has enough context to select and invoke this tool 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?

The schema has 100% description coverage for both query and limit, so the schema carries the parameter documentation burden. The description restates that query accepts name, email, or phone number, which aligns with the schema but does not add meaning beyond it.

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 searches the Mac's Contacts app (Contacts.app, local/iCloud) by name, email, or phone number, using the specific verb 'Searches' plus the exact resource. It also distinguishes itself from Microsoft 365 directory tools by explicitly naming alternatives.

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 explicitly tells the agent to use m365_search_contacts or search_m365_directory for Microsoft 365 directories, providing clear when-not-to-use guidance. It also implies this is the right tool for local/iCloud Contacts searches, establishing a clear usage context.

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