gmail_suggest_recipients

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

Annotations already cover read-only and idempotent safety, and the description adds genuinely new context: it is a local heuristic with no extra scopes required, and it never auto-sends to suggested addresses. That last caveat closes a real safety question an agent might have before inserting a suggestion into a draft.

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?

Four short clauses, front-loaded with what the tool returns and how it ranks. No filler and no repetition of the annotations.

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?

With only two parameters, no output schema and a terse input spec, the description should say what actually comes back (bare addresses? ranked pairs?) and how recency is bounded. "Frequency-ranked From headers" hints at the shape but leaves the return format underspecified.

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 only 50% — query is documented in-schema but max_results has no description beyond its bounds. The description clarifies that the query matches against recent-thread senders, which adds some semantic meaning, but it says nothing about how max_results limits the ranked output.

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 gives a specific verb and resource ("Suggests recipient addresses from recent threads") plus the mechanism (frequency-ranked From headers), which distinguishes it from a plain address-book lookup. It stops short of naming the closest sibling (contacts_search) as the alternative for directory-based lookup.

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 phrasing implies a compose-time use case, but the description never states when to prefer this over contacts_search or gmail_search_messages. There are no explicit exclusions or routing guidance, so the agent has to infer the entry point.

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