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 adds useful pricing, listing, free-preview, and prerequisite context, but the phrase 'Buy per-query access' creates mild tension with the read-only annotation even though it later says it returns fund instructions.

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-loads the core purpose, then supplies listing, price, preview alternative, and return behavior. It is mostly efficient, though the colon-heavy listing clause is slightly dense and the opening 'Buy' phrasing could be clearer.

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?

It explains the prerequisite, the listing and price, and that fund instructions are returned, which is enough to understand the flow. However, with no output schema, it does not describe what the fund instructions contain or how they relate to data_session_fund, leaving a meaningful gap for a payment-adjacent tool.

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?

There is only one parameter and schema coverage is 100%, so the schema fully documents session_id as a UUID from data_session_open. The description reinforces the data_session_open prerequisite but adds no additional parameter semantics beyond what the schema provides.

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 states a clear high-level purpose: obtaining paid per-query access to a live data listing, with a concrete listing and price. It distinguishes itself from data_preview as the free alternative, but does not clarify how it differs from the sibling data_session_fund, leaving some sibling ambiguity.

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 gives implied usage context: try data_preview first, then use this after data_session_open for paid access. However, it does not explicitly say when to use this versus data_session_fund or data_session_attach_escrow, so the agent must infer the correct funding route.

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