Get subscriber counts

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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful output behavior beyond that: it returns a total split into free and paid categories. This helps an agent understand what the response will contain, especially since there is no output schema.

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 one sentence and immediately states the core output and breakdown. There is no filler, and the most important information about what the tool returns is front-loaded.

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 low-complexity, read-only aggregate tool with no required parameters and rich annotations, the description is complete. It tells an agent exactly what metric is returned and how it is broken down, which is sufficient to invoke the tool correctly with no arguments.

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 single optional parameter is fully documented in the schema with a clear description of its behavior and default. The tool description does not repeat parameter details, but with 100% schema coverage, the schema carries the semantic weight. No additional parameter insight is needed.

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 states that the tool returns total subscriber counts, broken down by free and paid. The phrase 'how many subscribers do I have' explicitly frames it as an aggregate count, distinguishing it from sibling tools like list_subscribers or export_subscribers that deal with individual subscriber data.

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 gives a clear use case: use this tool when you need the total subscriber count, especially a quick answer to 'how many subscribers do I have'. It implies this is the right tool for aggregate counts rather than detailed subscriber lists, though it does not explicitly name alternatives or exclusions.

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