lookup_contact

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

No annotations are provided, so the description carries full responsibility. It implies a read-only lookup but does not explicitly state safety, behavior on no match, or whether multiple results may be returned. The description is minimal and lacks behavioral transparency beyond the basic action.

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 a single, concise sentence that conveys the purpose and expected output without unnecessary words. It is appropriately front-loaded with the action and resource.

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?

The tool is simple with one parameter and no output schemachers. The description covers the core functionality well, but it doesn't specify behavior for ambiguous cases (e.g., multiple matches, no match) or explicitly state read-only nature. Given the simplicity, a 4 could be argued, but the lack of any behavioral detail beyond the core action lowers it.

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 coverage is 100% — the parameter 'name' has a clear description with examples. The tool description does not add additional parameter semantics beyond what the schema already provides, so a baseline of 3 is appropriate.

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's function: looking up a contact in macOS Contacts to retrieve phone number or email. The verb 'Look up' is specific, the resource is identified (macOS Contacts), and the intended output is explicit. It distinguishes from siblings which are message-related.

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 implies the tool is for finding contact information but does not explicitly state when to use it versus alternatives, nor does it mention exclusions or prerequisites. Since all siblings are message-related, the context is clear, but explicit guidance is missing.

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