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

Annotations indicate readOnlyHint=false, idempotentHint=true, and destructiveHint=false; the description does not contradict these. It adds useful behavioral context: a financial transaction is platform-executed, per-query pricing is 0.01 USDC, and there is a free preview path via data_preview. This is valuable beyond the annotation fields.

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: the core action ('Buy per-query access') appears immediately, followed by the free preview pointer, listing specifics, and the post-funding query step. Every sentence contributes meaningful information; the minor typo 'Platform-executes' does not affect clarity or structure.

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 simple one-parameter tool, the description covers the key context: what is purchased, the cost, the free preview alternative, and the intended follow-up query action. The absence of an output schema is partially mitigated by the clear workflow references, though failure/refund behavior is not disclosed.

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%: the single session_id parameter is clearly defined as the UUID of a data session opened via data_session_open. The description adds workflow context but no additional parameter-level semantics, so baseline 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 clearly states the action: 'Buy per-query access to live data listings,' identifying the resource and the transactional nature of the tool. It also references data_preview and data_session_query to situate the tool within a workflow, though it does not explicitly differentiate it from the similar sibling data_session_funding_package or data_session_attach_escrow.

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 usage context: use preview for free first, then fund the session, then query. However, it does not explicitly state when to choose this tool over sibling alternatives like data_session_funding_package or data_session_attach_escrow, leaving some routing to inference.

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