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

Annotations already indicate a mutating operation (readOnlyHint false) and idempotency, so the bar is lower. The description adds concrete behavioral context: this actually moves money and buys per-query access at a stated price (0.01 USDC/query). It also clarifies that funding is platform-executed, which is useful beyond the annotation metadata.

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 compact sentences with no filler. It front-loads the purpose, then gives the concrete listing/price, then connects to the query action. Every clause contributes to an agent's decision-making.

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 full schema coverage, the description is nearly complete: it states cost, data source, prerequisite (data_preview), and downstream action (data_session_query). The main omissions are what the funding call returns and expected behavior if the session is already funded, but these are minor given the simple structure and existing annotations.

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 single session_id parameter is already documented as a UUID from data_session_open with the purpose 'funding-package / attach / query.' The tool description adds no additional parameter-level detail, 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 clearly states the verb and resource: 'Buy per-query access to live data listings' and 'Platform-executes funding so you can data_session_query.' It also distinguishes itself from data_preview (free taste) and data_session_query (post-funding use). However, it does not explicitly differentiate from the sibling data_session_funding_package, and it relies on the schema to clarify that it targets an existing session.

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 provides a clear usage sequence: try data_preview first for free, then fund the session, then use data_session_query. This gives an agent actionable context about when to call this tool relative to key siblings. It lacks explicit exclusionary guidance, but the flow is strongly implied and sufficient for a low-complexity tool.

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