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

Annotations already mark this as non-read-only, idempotent, and non-destructive. The description adds meaningful behavioral context: this is a paid purchase with a concrete price (0.01 USDC/query), and the platform executes funding on the user's behalf. That clarifies the financial consequence beyond what the annotations express.

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?

Three short sentences front-load the main action and include the listing, price, and follow-up tool. The wording is slightly informal with phrases like 'first taste free', but it remains efficient and focused.

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 rich annotations, the description provides enough context to invoke it correctly: what it costs, that it requires a session, and what to do afterward. It does not describe the return value or failure conditions, but that gap is minor given the tool's simplicity and lack of output schema.

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 single parameter session_id is already fully described in the schema, including its format, origin from data_session_open, and purpose. The description adds no parameter-level detail, but the schema coverage is 100%, so the baseline of 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 clearly states the tool buys per-query access to live data listings, names the specific listing, and explains the ultimate goal of enabling data_session_query. It does not explicitly differentiate itself from sibling tools like data_session_funding_package or data_session_attach_escrow, but the core action is unambiguous.

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 an implicit workflow: use data_preview for a free taste first, then fund this session, then call data_session_query. This is useful context. It does not explicitly state when to choose this over funding_package or attach_escrow, so it stops short of full alternative routing.

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