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

Beyond the annotations, the description discloses that this is a paid/prepaid operation that returns a purchase receipt, requires an API key, is not guest-callable, and has a sandbox receipt mode. These are meaningful behavioral details not available from the annotations or schema. It does not fully explain failure modes or what happens on insufficient funding, but the core transactional behavior is transparent.

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 dense but every sentence earns its place: purpose and free alternative, authentication requirements, core behavior and return, sandbox behavior, guest exclusion, and the REST endpoint. It is front-loaded with the primary purpose and avoids 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?

For a paid, auth-requiring, receipt-producing tool with no output schema, the description covers purpose, prerequisite funding, authentication, sandbox behavior, return value, and REST endpoint. The main gap is the underspecified parameters, especially k and delivery_receipt, which prevents this from being fully complete.

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 description helps with session_id indirectly and explicitly explains sandbox_receipt, but it leaves query, k, and delivery_receipt semantically underserved. With schema description coverage at only 40%, the description needed to compensate for those gaps, and it does not explain what k controls or what delivery_receipt should contain.

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 action ('Buy per-query access', 'Run a prepaid query') and a clear resource ('data session'), and it explicitly names data_preview as the free alternative. This differentiates the tool from its siblings and makes its role in the paid data-access flow unambiguous.

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 provides explicit usage context: it requires an agent API key, is not guest-callable, runs against a funded data session, and points to data_preview as the free 'first taste' alternative. This tells an agent when to invoke this tool versus the closely related preview and session-management siblings.

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