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

Beyond destructiveHint it discloses that this sends a real email people will receive and that it 'cannot be undone' — genuine impact context. The confirm-required gate is only in the schema, and rate limits/permissions aren't discussed, so not a 5.

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?

Front-loads 'WRITE, SENDS EMAIL' and irreversibility in two dense lines with no filler. The trailing API endpoint notation is mildly redundant for an agent but harmless.

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?

For a 7-parameter mutation with no output schema, the description plus rich schema covers what's needed: the destructive nature, the mode selection, and full parameter docs. Only the confirm gate and permission requirements live solely in the schema.

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 the schema already documents hash_key, confirm, recipients, subject, message, attachment and blind_copies in detail. The description only implies the default/custom split that those parameters implement, adding little on top of the schema.

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 and resource: 'email a payment reminder for an invoice', with the two modes (default template vs custom) named. It is clearly distinct in practice from send_invoice or send_estimate, but never explicitly contrasts with those siblings, so it stops short of a 5.

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?

Explains the default-vs-custom delivery choice and that results cannot be undone, which tells the agent when to supply custom fields. It does not explicitly say when to prefer this over siblings like hiveage_send_invoice or hiveage_get_invoice, so no exclusions.

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