Send Email Batch

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

Beyond annotations (readOnlyHint=false, destructiveHint=true), the description adds crucial behavioral context: HTTP 200 returned even when individual messages fail, requiring per-message ErrorCode/Message inspection. It also explicitly states the read-only block condition, aligning with the destructive annotation.

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?

Three concise sentences, front-loaded with the core action and limit. No wasted words, and essential behavioral warnings are included without bloat.

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?

Despite having an output schema, the description wisely calls out the non-obvious behavior that HTTP 200 does not imply per-message success. It also covers the batch size limit, field-name expectation, and read-only restriction. This is sufficient for a moderate-complexity batch tool.

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 schema already provides high coverage (100%) for the single 'messages' parameter, describing Postmark field names and the 500-message limit. The description adds little parameter-specific meaning beyond 'individually-composed,' which is somewhat redundant with the schema's 'message objects' detail. The return-value note does not directly enhance parameter semantics.

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 uses a specific verb ('send') with a clear resource ('email batch') and scope ('up to 500 individually-composed emails'). It distinguishes from siblings like 'send_email' and 'send_email_batch_with_templates' by emphasizing individual composition rather than templates or single sends.

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 clearly implies use for batch email sending (up to 500) and explicitly warns about read-only block. It does not explicitly name alternatives or state when not to use, but the context is clear given sibling tool names and the 'individual' qualifier.

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