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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description discloses that this is a paid, prepaid operation requiring authentication and not guest-callable, and explains the sandbox_receipt signing behavior for testnet wallets. It does not fully detail side effects like balance consumption or failure state, but it adds meaningful behavioral context beyond 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?

Four short sentences, each earning its place: purpose, free alternative, auth prerequisite, operational behavior, sandbox option, guest-callable restriction, and REST endpoint. The key paid-vs-free distinction 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?

For a paid query tool with no output schema, the description gives a high-level return concept ('attested hits plus a purchase receipt') and invocation prerequisites. However, it leaves k and delivery_receipt unexplained and does not specify billing/consumption side effects, so an agent may still be uncertain about the full invocation contract.

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 compensates only for sandbox_receipt and gives high-level meaning to query/session_id. It does not explain the optional k parameter or delivery_receipt, so an agent cannot fully understand the input surface from either source.

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 verb and resource: 'Buy per-query access to live data listings' and 'Run a prepaid query against a funded data session' with the REST path. It also distinguishes itself from the sibling by explicitly pointing to data_preview as the free first taste, making the tool's paid scope clear.

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 clearly states the need for an agent API key, a funded data session, and that the tool is not guest-callable, so an agent knows the prerequisites. It names data_preview as the free alternative, though it does not explicitly list data_session_open/fund as prerequisite steps or state when not to use this tool.

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