transactional_email_send

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, yet it discloses almost nothing beyond the mechanism. It does not state that this is a mutating, non-idempotent send, whether it requires a valid API key (the apiKey/restEndpoint params hint at auth but the description never says so), what happens on duplicate sends, or any rate/error behavior.

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, with the core action front-loaded and no padding. The second sentence is useful for orientation but ends in a vague 'etc.' that adds little precision.

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?

This is a 6-parameter mutation tool with a nested recipient object, no output schema, and no annotations. The description should at minimum cover auth requirements, the campaign prerequisite, and send semantics, but it covers none of these, leaving the agent under-equipped to invoke it correctly.

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 campaign_id, recipient, apiKey, restEndpoint, external_send_id, and trigger_properties. The description adds no parameter-level meaning (e.g., that external_send_id enables idempotency or that trigger_properties feed personalization), so the 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?

The description names a specific verb and resource ('Send a transactional email') and adds the mechanism ('via an API-triggered campaign'), which tells the agent a pre-configured campaign is required. It does not distinguish itself from close siblings such as messages_send, campaigns_trigger_send, or canvas_trigger_send, which an agent could easily confuse it with.

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?

'Used for order confirmations, password resets, etc.' gives example scenarios, which implies the usage context, but there is no explicit when-to-use/when-not, no prerequisites, and no named alternative among the many sibling send tools. The agent must infer selection criteria on its own.

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