List stats for a subscriber

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false. The description's 'Reads account data' adds no meaningful behavioral context beyond what the annotations already convey, and it omits details like pagination, rate limits, or return format.

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 brief and front-loaded with the core action. The second sentence ('Reads account data') is somewhat redundant given the readOnly annotation, but it does not bloat the text significantly.

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 4-parameter tool with no output schema and only 50% schema description coverage, the description is too sparse. It does not explain the two undocumented date parameters, the account selection behavior, or what the stats contain.

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 only 50%; email_sent_after and email_sent_before lack schema descriptions. The description does not mention any parameters or compensate for those undocumented date filters, leaving their semantics unclear.

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 verb ('List') and resource ('stats for a subscriber'), making the purpose clear. However, it does not explicitly differentiate itself from sibling stats tools like get_email_stats or get_growth_stats, so it falls short of a 5.

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 provides no guidance on when to use this tool versus alternatives such as get_email_stats, get_growth_stats, or get_subscriber. There are no when-to-use or when-not-to-use conditions stated.

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