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

Annotations already cover the safe read-only, idempotent, non-destructive profile. The description adds meaningful behavioral context: it spans every inbox in a shared account, includes pagination details (next_page_token), and enumerates the return fields, going beyond what annotations convey.

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 information-dense and well-structured: purpose first, then return shape and pagination, then scope caveat and sibling routing. It is slightly long but every sentence earns its place; no redundancy.

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?

Given the tool's complexity (11 params) and the existence of an output schema, the description fully equips an agent to call it correctly: it explains the scope, pagination, return fields, and the critical sibling distinction. Nothing essential is missing.

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 parameters are already documented. The description only adds the pagination token context and the field list, which aligns with the output schema but does not enrich parameter meaning beyond what the schema provides.

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 clear verb+resource: 'Lists conversation threads across every inbox in the account.' Explicitly distinguishes from the inbox-scoped sibling get_agentmail_inbox_threads by naming the organization-wide scope and the alternative for single-inbox use.

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?

Provides explicit routing guidance: 'the inbox-scoped twin get_agentmail_inbox_threads is the one to use when a single inbox is meant.' Also warns that this reaches inboxes other callers created, which informs when to avoid it for isolated operations.

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