Find a contact / address

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

Annotations already establish readOnly/idempotent/non-destructive/openWorld, so safety is covered. The description adds genuinely useful behavioral context: results merge address books with mail history, history is query-dependent, and an omitted query dumps the entire address book rather than failing. It stops short of describing result ordering or result caps.

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?

Front-loaded with the core action, then the two sources, then the usage trigger and default behavior. Three sentences with no filler, though the parenthetical about shared address books and the closing default-behavior sentence could be compressed slightly.

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 read-only lookup with no output schema and fully documented parameters, the description covers what the tool searches, when to reach for it, and the no-query fallback. Missing only result shape/ordering details, which are minor here.

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 description coverage is 100%, so all four parameters are already documented, including that include_history requires a query. The description reinforces the query-optional semantics but adds no syntax or value-format detail beyond the schema. Baseline 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?

States a specific verb and resource ('Finds an e-mail address or phone number') and names the two data sources it spans: address books (own and shared) plus mail history. This clearly separates it from siblings like mail_search_emails (message content) and mail_add_contact (mutation).

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?

Gives a clear when-to-use trigger ('whenever you need a person's or company's address before sending anything') and explains the no-query behavior. It does not explicitly contrast with mail_search_emails for the ambiguous case of looking someone up by message content, but the context is otherwise unambiguous.

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