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

Annotations already provide idempotentHint=true, readOnlyHint=false, and destructiveHint=false, so the safety profile is known. The description adds that this is a paid, platform-executed funding action, which helps, but it does not clarify charge mechanics, session state changes, or any limitations beyond the listed price.

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 core purpose. The listing, price, free-preview pointer, and downstream query step all earn their place without unnecessary filler.

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 single-parameter tool with no output schema, the description plus schema provide the essential details: existing session required, paid access, listing, price, and next step. The main omission is clarifying how this relates to data_session_funding_package and data_session_attach_escrow, but that is not critical for invoking the tool correctly.

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 100%, and the only parameter, session_id, is already well described as a UUID from data_session_open. The tool description does not need to add parameter details and does not add any, which matches the baseline for fully covered schemas.

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 action: buy per-query access to live data listings for a specific session, then query. It names a concrete listing and price, and points to data_preview for the free alternative. It does not explicitly differentiate from data_session_funding_package or data_session_attach_escrow, so it stops short of full sibling differentiation.

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 gives a clear workflow context: try data_preview first for free, then fund access, then use data_session_query. This implies when the tool is appropriate without stating exclusions or naming every alternative. It does not mention data_session_funding_package or data_session_attach_escrow, but the basic usage sequence is clear.

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