list_emails_metadata

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

Clearly describes behavior beyond annotations (none provided): notes it returns only metadata fields and does NOT return preview or body-derived content, providing full transparency for privacy-sensitive use.

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 paragraph with no wasted sentences, front-loaded with the key distinction. Slightly long but every part adds value; could be trimmed slightly but remains efficient.

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 3 parameters and no output schema, the description adequately explains return values (metadata fields), use cases, and relation to siblings. Does not detail paging mechanics but inherits from list_emails. Completeness is high for the tool's simplicity.

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% (baseline 3). The description adds no new parameter detail beyond what is in the schema; it only rephrases 'mailboxId' as 'optionally filtered by mailboxId' and mentions paging/sort, which are already explicit in schema properties.

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 lists emails but returns only metadata fields, distinguishing it from the sibling 'list_emails' by specifying the exact fields returned and the omission of body-derived content.

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?

Explicitly states when to use: 'privacy-sensitive flows where the workflow needs only the envelope' and provides an alternative suggestion: 'pair with get_email_metadata for follow-up lookups that should also stay header-only.'

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