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

Annotations already declare readOnly/non-destructive, so the bar is lower, yet the description still adds real value: the link expires in 1 hour, it mirrors the dashboard's Export output, and it requires a Cotlet API key with access. That auth and expiry context is exactly what annotations can't express.

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?

Front-loaded and otherwise tight, but the 1-hour validity fact is stated twice ('valid for 1 hour' and 'The link stops working after 1 hour'), so one sentence does not earn its place. That redundancy is a concrete structural flaw.

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 no parameters and no output schema, the description carries the return-value burden and does so: it explains the output is a CSV download link, its expiry window, and the credential needed. Nothing an agent needs to call this correctly is missing.

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 tool takes zero parameters, so there is no parameter semantics to explain and the baseline is 4. The description correctly focuses on the return artifact rather than inventing input details.

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 (export) and resource (subscribers), and names the exact artifact produced: a CSV download link. It explicitly distinguishes itself from list_subscribers, so an agent can route correctly without opening either schema.

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?

Gives a direct when-to-use rule ('Use it for the full list') and names the alternative with the condition that selects it ('list_subscribers is better for filtered pages'). This is explicit routing guidance, not inference.

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