send_email

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

No annotations are provided, so the description carries the full behavioral burden, and it discloses almost nothing beyond the action itself. It does not mention that sending is an irreversible external side effect, that `from` must be on a verified domain, that idempotency_key deduplicates retries, or that send_at defers delivery — all facts an agent needs to act safely.

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 short sentences, purpose front-loaded, with the required payload constraint immediately after. No filler, though the second sentence could carry slightly more information at the same length.

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 13-parameter mutation tool with zero annotations and no output schema, the description is thin: it is silent on verified-domain prerequisites, rate limits, scheduling, idempotency behavior on retry, and the single-vs-batch choice. An agent could call it correctly only by reading the schema closely, which leaves real risk around side effects.

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% and the property descriptions are well written (verified domain, ISO 8601, template alias semantics). The description restates the body/template alternative already implied by those property descriptions, so it adds only marginal value; 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 and resource ("Send a transactional email"), which is immediately actionable. It does not distinguish itself from the sibling send_batch_emails, so an agent choosing between single and batch sending gets no help here.

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 second sentence gives conditional guidance on payload shape ("Provide html_body and/or text_body, or template_alias with template_data"), which is genuinely useful for constructing a call. However, there is no guidance on when to use this versus send_batch_emails, when scheduling via send_at is appropriate, or any preconditions such as a verified sending domain.

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