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

The description states it is a 'prepaid query' and mentions a per-query cost, making clear that it consumes funds. It does not detail side effects like delivery receipt signing, but the overall behavior is adequately disclosed and consistent with the annotations (readOnlyHint=false).

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 compact and front-loaded with the essential purpose, pricing, and sequence. It avoids fluff but includes a few extra details (max queries, price) that are useful for decision-making. Slightly dense but not verbose.

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 gives enough context to understand the tool's role in the session flow and its cost model, but it omits expected output format, error handling (e.g., insufficient funds), and any prerequisite details beyond the sequence. The missing parameter explanations also reduce completeness.

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 schema only documents session_id and sandbox_receipt. The parameters k and delivery_receipt are left unexplained, and the schema-level description only says 'REST body + session id.' This leaves significant ambiguity about what k controls and what delivery_receipt is for, especially since these are optional and not self-explanatory.

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 verb ('Buy per-query access'), the resource ('live data listings'), and explicitly names the sibling data_preview as the free alternative. It also gives concrete pricing and a session limit, making the tool's purpose unmistakable.

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 the required sequence (data_session_open → data_session_fund → data_session_query) and clarifies that this is a prepaid query against a funded session, implicitly telling the agent when to use it. It doesn't explicitly list when not to use it beyond mentioning the free preview, but the sequence is sufficient guidance.

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