Find newsletters & mailing lists

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior: default scope is ALL connected accounts, and results are aggregated per sender rather than returning raw messages. It does not mention cost/latency of scanning multiple accounts, which is the one remaining behavioral gap for an openWorld read.

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?

A single dense sentence that front-loads the core scope and folds the default-scope caveat and the usage cue in afterward. No redundant restatement of the title or 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?

There is no output schema, so the description carries the burden of explaining returns — it does so by specifying sender-level grouping with counts, unread counts, and unsubscribe support. Combined with the fully documented inputs, an agent has everything needed to call it and interpret results.

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% and every parameter (top, days, account, scanPerAccount) is documented in the schema itself. The description only reinforces the account default ("across ALL accounts by default"), adding little beyond structured data — baseline 3 applies.

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 (list) and a precisely scoped resource (newsletters, mailing lists, marketing senders), plus the aggregation model (grouped by sender with counts, unread counts, one-click unsubscribe flag). This clearly separates it from search_emails or inbox_summary without needing to open any schema.

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?

"Use before cleaning up or unsubscribing" gives an explicit usage context tied to a workflow the sibling bulk_cleanup serves. It does not name an alternative for the adjacent 'find a specific sender's mail' case (search_emails), so it stops short of full when/when-not routing.

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