Send Email Batch With Templates

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

Annotations already mark destructiveHint=true and readOnlyHint=false, but the description adds valuable behavior details: returns one result per message, instructs to inspect each element's ErrorCode/Message, and notes that the tool is BLOCKED in read-only mode. This provides actionable context beyond the structured fields without contradicting them.

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 three concise sentences, each serving a clear purpose: stating the core function, explaining the response format, and warning about read-only mode. No redundant or filler content; information is front-loaded with the primary action.

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 that an output schema exists, the description does not need to detail return fields beyond the critical note about per-message ErrorCode/Message. The 500-message limit, template-rendering capability, and read-only block are all covered. The description is sufficient for an agent to select and invoke this tool correctly relative to its siblings.

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?

The input schema has 100% parameter description coverage for the single 'messages' field, including explanation of nested objects (TemplateId/TemplateAlias, TemplateModel, From/To). The tool description does not add additional parameter semantics, but none are needed because the schema is thorough. 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: 'Send up to 500 template-rendered emails in one request.' This specifies the verb (send), resource (emails), and key constraints (batch, template-rendered). It also distinguishes from siblings like send_email_batch (which lacks template rendering) and send_email_with_template (which sends a single message).

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 implies use cases: sending multiple template-based emails efficiently in a single API call. It gives a clear context (batch + templates) but does not explicitly exclude alternatives like send_email_batch (non-template) or send_email_with_template (single). Since sibling names alone provide strong differentiation, this is a minor omission.

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