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

Annotations only flag a mutating, non-idempotent operation; the description adds real behavioral context by disclosing cost per query (0.01 USDC), a session cap (max 5 queries/session), and the consumption-oriented act of paying for access. It does not mention receipt signing or failure behavior, but the annotations lower the bur and this is meaningfully beyond what they state.

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 sentences with no filler; the action, price, limit, and prerequisite sequence are each packed into a concise line. The most decision-relevant information (cost and precondition) appears early, and every sentence earns its place.

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 description covers the core workflow (open → fund → query) and the cost model, which is the essential context for a paid query tool. However, it does not explain how results are returned, the role of delivery_receipt/sandbox_receipt, or the purpose of k, and there is no output schema to shoulder that burden. It is adequate but has clear gaps.

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%: session_id and sandbox_receipt are documented in the schema, but k, delivery_receipt, and query are not. The main description adds no parameter-level meaning for these, so it does not compensate for the low coverage and leaves agents guessing about k and delivery_receipt.

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 names a specific action ('buy per-query access to live data listings') and identifies the exact listing, pricing, and query limit, which distinguishes it from the sibling data_preview. It is slightly indirect because the tool actually executes a prepaid query against a funded session; the clearer verb appears in the input schema description rather than the main description.

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 explicitly names data_preview as the free alternative and provides the required sequence data_session_open → data_session_fund → data_session_query, telling an agent when this tool is appropriate. It does not explicitly state when not to use it or compare against other paid-work siblings, so one point is deducted.

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