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

Annotations already declare read-only, idempotent and non-destructive behavior, so the safety profile is covered. The description adds genuinely non-obvious operational context that annotations cannot express: the tool is a phase-2 stub and will yield an empty result. It does not say whether that manifests as an empty array or an error, which is the remaining gap.

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 the purpose front-loaded and the availability caveat immediately after. No filler or redundancy; every sentence carries information an agent needs.

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 no-argument list tool with full annotation coverage and no output schema, the description supplies what matters most: that the call is currently a no-op. It could be slightly more complete by stating the expected response shape (empty list versus an error), but nothing essential 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 for the description to carry; the baseline for a parameterless tool applies. Nothing in the description is needed to clarify calling conventions.

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 states a specific verb and resource ("Lists subscriptions"), which is unambiguous about what the tool does. It does not explicitly contrast itself with the many other list_* siblings, but the resource noun is distinct enough that confusion is unlikely.

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?

It gives a strong, explicit when-not-to-use signal: the tool is unavailable until phase 2 and returns no records in this build, which effectively tells an agent to avoid calling it. It stops short of naming an alternative route for obtaining subscription data.

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