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

Annotations already declare readOnlyHint and idempotentHint, so the description appropriately focuses on additional behavioral context: it returns the 'most recent' subscription, implying historicity and a possible absence of subscription. It does not cover edge cases like errors, but given the output schema exists and the safety profile is already annotated, this is sufficient.

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, efficiently structured sentence. The verb and resource are front-loaded, and every word contributes meaning—no redundancy or filler.

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 has no parameters, an output schema that covers return values, and annotations that handle safety, the description fully covers what an agent needs: what it returns, for whom, and the specific subscription fields. 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?

With zero parameters, the schema coverage is trivially 100%, and the description correctly does not need to explain parameters. The baseline for no parameters is 4, and there is nothing to add beyond the already-clear schema.

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 uses a specific verb ('Return') and resource ('signed-in user's most recent Convex Lake subscription'), and even lists the key fields returned (status, renewal, cancellation state). This clearly distinguishes it from sibling tools like get_profile or the file/data getters, so an agent can understand its purpose without ambiguity.

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 implies usage context—it returns subscription details for the current signed-in user—but does not explicitly state when to use it instead of alternatives like get_profile. Since no confusion is likely given the clear resource name, this is adequate but not fully explicit, earning a 4 rather than a 5.

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