get_metrics

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

With no annotations provided, the description carries the burden. It correctly implies a read operation and describes the data returned. However, it does not explicitly state that it is non-destructive or indicate any side effects.

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 a single, well-structured sentence that lists the resource and scope upfront. It contains no extraneous words and efficiently communicates the tool's function.

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 simplicity (3 optional parameters, no output schema), the description provides a reasonable outline of the return values (totals and daily series). It could be slightly improved by noting the response format, but is largely sufficient.

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 already provides descriptions for all three parameters (100% coverage). The description adds minimal extra value beyond summarizing the date bounds. The sender parameter is not elaborated beyond what the schema states.

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 lists the specific metric types (send, delivery, bounce, complaint, open, click) and indicates both totals and daily series. It implicitly distinguishes from sibling tools like get_campaign_metrics by focusing on aggregate, not campaign-specific, metrics.

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 the optional date bounding, giving context for when to use the from/to parameters. However, it does not provide explicit guidance on when to prefer this tool over siblings, such as get_campaign_metrics or list_emails.

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