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

Annotations already declare destructive, non-idempotent, and open-world behavior, so the safety profile is covered. The description adds valuable context beyond annotations by noting the owner approval gate before the message is sent.

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 no waste, front-loading what the tool does and then the key approval behavior.

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?

With full schema descriptions and annotations, the definition is nearly complete for invocation. It clearly covers sending channels, recipients, and approval, though it could mention the related estimate/preview sibling or what the approval response looks like.

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 parameters are already well documented. The description reinforces the channel options and recipient targeting but adds no syntax, defaults, or other detail beyond the schema.

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?

States a specific action and resource: sending one message to chosen clients via email, SMS, or push. It is clearly distinguishable from read/list siblings, though it does not explicitly distinguish from estimate_message_blast.

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?

Adds an important precondition that the send waits for the owner's approval, which implies a review workflow. However, it does not explicitly say when to use this versus estimate_message_blast or how to preview recipients before sending.

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