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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the description's lack of explicit safety caveat is acceptable. However, the description does not add behavioral context beyond the annotation: it doesn't mention response details (e.g., whether it returns boolean, subscription info), or if any edge cases (e.g., invalid addresses) exist. It adds minimal value beyond the annotations.

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 concise sentence that clearly conveys the tool's purpose. It is front-loaded and has no unnecessary words 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's simplicity (two simple parameters, both documented, with a clear purpose), a single sentence is likely sufficient. The output schema exists, so return details are covered by that. However, the description could benefit from telling the agent whether the tool returns a boolean, status, or detailed subscription info, but that may be unnecessary given the output schema. It's minimally complete but not rich.

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 100%, and each parameter has a clear description ('Subscriber Ethereum address', 'Publisher Ethereum address'). The tool description rephrases the parameters but doesn't add deeper semantic context (e.g., how these addresses are used, what format is expected beyond '0x...', or any relationship to the subscription). Since the schema already covers the parameters, the description adds little extra semantic value.

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 the action ('Check if an address is subscribed'), the specific resource (a subscription on PayPerByte), and the key entities (address and publisher). It distinguishes itself from siblings like byte_list_my_subscriptions (which lists current user's subscriptions) and byte_subscription_health (which likely assesses health).

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?

While the description implies the tool is for checking a specific subscription status given an address and publisher, it does not provide explicit guidance on when to use this versus alternatives like byte_list_my_subscriptions, byte_subscription_health, or byte_get_token_balances. No exclusions or alternative suggestions are given.

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