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

The description discloses the cost (0.01 USDC/query), states that funding is platform-executed, and clarifies the outcome (enables data_session_query). Annotations already cover idempotency and non-readonly behavior, and the description adds useful context without contradicting them.

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 two sentences and front-loads the core action, price, and free-preview alternative. The nested listing phrase is slightly dense but contains no redundant 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?

The description explains the core transaction and outcome, and the schema covers the session_id requirement. However, it does not address the relationship to data_session_funding_package or data_session_attach_escrow, which are relevant siblings for a financial funding action.

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, session_id, and the input schema already provides a full description at 100% coverage. The tool description adds no additional parameter-specific meaning, so the baseline score of 3 is appropriate.

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 uses a specific verb ('Buy per-query access') and names the exact listing being purchased. It is mostly clear, but it does not explicitly distinguish itself from the sibling tool data_session_funding_package, which could confuse an agent selecting between funding-related tools.

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 implies a usage flow: try data_preview for free, then fund, then use data_session_query. However, it provides no explicit guidance on when to use this tool versus data_session_funding_package or data_session_attach_escrow.

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