search-contacts

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

With no annotations, the description carries full burden and does well by disclosing that it reads the macOS Contacts database directly, requires Full Disk Access, and does not require Contacts.app or Apple-Events grant. It also states return fields. Minor gaps: doesn't mention whether it is read-only explicitly or handle errors, but overall clearly describes behavior.

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 well-organized with clear 'Use when', 'Reads...', 'Returns...', and 'Do not use when' segments. Every sentence adds valuable information, no fluff, and it is appropriately sized for the tool's simplicity.

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 search tool with one parameter and an output schema, the description covers all essential aspects: use case, when not to use, access method, prerequisites, and return values. There is no ambiguity about the tool's function or limitations.

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 'query' is given meaning by the description: it can be a name, organization, nickname, or email. This goes beyond the schema's generic 'string' definition and fully compensates for the 0% schema coverage.

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 clearly what it does: looking up a person in Contacts by name, organization, nickname, or email to find email addresses and phone numbers. It uses a specific verb ('search') and resource ('Contacts'), and explicitly distinguishes from sibling tool search-messages by saying 'Do not use when: searching email messages...'.

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?

Explicit 'Use when' and 'Do not use when' sections provide clear guidance on when to choose this tool over alternatives, including naming the alternative (search-messages). It also gives prerequisites (Full Disk Access, no need for Contacts.app running), which helps agent decide when this tool is viable.

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