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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description usefully adds that the call returns fund instructions rather than transferring funds, which softens the 'Buy' phrasing, but it says nothing about the payment/auth step itself.

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?

It is a single front-loaded sentence with the key action first and the price/listing detail after; no padding. The listing name and pricing clause make it slightly dense but nothing is wasted.

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 one-parameter tool with no output schema and full annotation coverage, the description supplies the missing pieces: the listing identity, the price, the free preview path, and the sequencing after data_session_open. It stops short of explaining what the fund instructions look like or the downstream escrow flow.

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 coverage is 100% and the single session_id parameter is fully documented in the schema, including its origin ('from data_session_open'). The description adds nothing about the parameter, so the baseline 3 applies.

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 even names the concrete listing and its price, so the resource is unambiguous. It does not, however, differentiate itself from close siblings like data_session_fund or data_session_attach_escrow, which an agent would need to choose between.

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 routes a browsing agent to data_preview ('first taste free') and states that fund instructions come back 'after data_session_open', implying the required ordering. There is no explicit when-not or comparison against data_session_fund / data_session_attach_escrow, so usage is only implied.

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