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

Annotations already declare readOnlyHint=false and non-idempotent, so the mutating nature is covered. The description adds real behavioral context beyond that: a per-query price (0.01 USDC), a session cap (max 20 queries/session), and the requirement that the session be funded first. It does not cover what happens on insufficient balance or failed delivery.

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?

Three short sentences, front-loaded with the paid-access purpose before the listing specifics and the required sequence. No redundancy, though the listing-specific pricing detail is arguably session data rather than tool behavior.

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 financially-gated, non-idempotent operation with five parameters and no output schema, the description covers the workflow and cost but omits return shape discussion and most parameter meaning. Adequate but with clear gaps an agent would want filled.

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% and the description explains none of the five parameters: 'k' (likely result count), 'query', 'delivery_receipt', and 'sandbox_receipt' are all left to the schema, two of which carry no per-field description at all. Since coverage is below 50%, the description needed to compensate and does not.

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?

States a specific verb and resource — buying per-query access to live data listings within a data session — and names the free sibling (data_preview) plus the prerequisite chain. It is slightly muddled by promotional framing ('first taste free') and the concrete action of running a query is somewhat buried, but an agent can still distinguish this from data_preview and data_session_fund.

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?

Explicit prerequisite ordering (data_session_open → data_session_fund → data_session_query) tells the agent exactly when this tool becomes callable, and data_preview is named as the free alternative. It lacks an explicit 'do not use if...' condition, but the sequencing guidance is strong.

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