set_mailbox_defaults

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

With no annotations, the description carries the burden. It discloses that setting defaults affects outbound sending behavior ('sending without a mailbox uses the configured outbound default'), but it does not mention permissions, rollback, or side effects. Adequate but could be more detailed.

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?

Two sentences with zero waste. First sentence states the action and scope; second provides prerequisite and rationale. Ideal conciseness.

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 simplicity (no output schema, few parameters), the description covers the prerequisite (list_mailboxes) and the use case. Could mention that it updates project settings, but it is complete enough for effective use.

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%, so the schema already documents all parameters. The description adds little beyond naming the parameters; it reinforces the ability to set 'null to clear' but that is already in 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?

The description clearly states the action 'Set' and the resources ('default_outbound_mailbox_id and/or auth_sender_mailbox_id') for a project. It distinguishes from sibling tools by mentioning the prerequisite to 'Use list_mailboxes first' and hints at the reason for setting defaults.

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 description provides clear context: use after list_mailboxes to choose an ID. It does not explicitly state when not to use or list alternatives, but it gives sufficient guidance for typical usage.

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