Send Email With Template

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

The description adds behavior beyond the annotations: it discloses the read-only mode block, the template selection constraint, and that the subject is derived from the template. This complements the annotations (readOnlyHint=false, destructiveHint=true) without contradicting them. It does not cover all side effects, but the annotations already signal destructive potential.

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 compact and front-loaded, with every sentence serving a purpose: the main action, the key parameter constraint, and a critical behavioral note. No unnecessary words or redundancy.

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 complexity (15 params, nested objects) and the presence of an output schema and annotations, the description covers the most complex parts: template selection and the read-only block. The schema handles required params like from_email, to, and template_model with its own descriptions. Slight shortfall is that it doesn't summarize the full parameter list or mention the output behavior, but the output schema mitigates that.

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 only 33%, so the description must compensate. It adds important meaning for template_id/template_alias by explaining the XOR constraint and that the subject comes from the template. However, many other parameters (cc, bcc, tags, headers, tracking options) are left to their names alone, and the description does not clarify them. Partial compensation only.

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 starts with 'Send a single email rendered from a stored template,' which uses a specific verb and resource while distinguishing this tool from siblings like send_email and send_email_batch. It clearly indicates the scope (single email) and the method (stored template).

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 states that exactly one of template_id or template_alias must be provided, and that the subject comes from the template. It also notes the tool is BLOCKED in read-only mode. This gives clear context for when to use it, but it does not explicitly mention alternatives or when not to choose this tool over send_email or batch variants.

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