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

Beyond the annotations' destructive/open-world flags, the description adds important behavior: per-email results in input order, batch-wide dry_run and duplicate protection, and pending_approval plus approval_url handling. These are non-obvious operational details that materially help an agent invoke the tool correctly.

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, beginning with the core batch-send purpose before adding result ordering, duplicate protection, and approval behavior. Every clause contributes operational information without redundant restatement.

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 complex batch mutation with no output schema, the description supplies essential context about per-email ordered results and approval behavior. It does not fully describe the success result object, but the schema, annotations, and approval note together make it sufficiently callable.

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?

With 75% schema description coverage, the schema already documents many fields, but the description adds batch-level meaning: the emails array mirrors send_email's fields, and dry_run/duplicate protection apply to the whole batch. It does not explicitly explain idempotency_key, but the schema covers that adequately.

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 states a specific verb and resource: sending up to 100 independent emails in one call, with each item mirroring send_email fields. This clearly distinguishes the batch operation from the single-email sibling send_email.

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 makes the batch-of-up-to-100 use case clear and references send_email for field parity and shared dry_run/duplicate semantics, implying when to use this instead of a single send. However, it never explicitly states the inverse condition or names validate_email as an alternative.

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