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

Annotations provide no behavioral hints (all false), so the description carries the full burden. It discloses that it is a purchase (buy per-query), requires authentication, returns a receipt, and has a sandbox mode. It doesn't mention idempotency or side effects beyond the purchase, but the transactional nature is evident.

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 well-structured: it opens with the core purpose, then prerequisites, behavior, a specific option, access restrictions, and the REST endpoint. Each sentence adds value, and the most important information is front-loaded.

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?

The tool has 5 parameters, no output schema, and complex transactional behavior. The description covers the main purpose, auth, and sandbox_receipt, but omits explanations for k, query, and delivery_receipt, and does not define 'attested hits'. Given the low schema coverage, these gaps make the description incomplete for a reliable call.

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 only 40% (2 out of 5 parameters). The description adds meaning only for sandbox_receipt, but does not clarify query, k, or delivery_receipt. Since coverage is low, the description should compensate, but it fails to explain the purpose of these parameters, leaving the agent without sufficient guidance.

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 tool's function: buying per-query access to live data listings and running prepaid queries against a funded data session, returning attested hits and a purchase receipt. It distinguishes itself from siblings like data_session_open and data_session_fund by focusing on the query step, and explicitly mentions data_preview as a free alternative.

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 provides explicit usage guidance: requires an API key, is not guest-callable, and implies the need for a funded session. It also directs users to data_preview for a free taste and explains the sandbox_receipt option. While it doesn't explicitly state when not to use it versus other session tools, the prerequisite of a funded session is clear.

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