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

The description adds useful behavioral context by noting the tool 'Returns fund instructions after data_session_open' and that preview access is available via data_preview. The readOnlyHint and idempotentHint annotations already cover safety, and the description does not directly contradict them, though the 'Buy' phrasing is potentially misleading because the tool appears to return instructions rather than execute a purchase.

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 brief and front-loaded with the main purpose, including pricing and the free preview alternative. It is slightly dense with commercial details, but there is no filler or unnecessary repetition.

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 strong annotations and full schema coverage, the description is mostly adequate. However, there is no output schema, and the description stops at 'Returns fund instructions' without explaining what those instructions look like or that the next step is likely data_session_fund, leaving some operational ambiguity.

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 coverage is 100%, and the only parameter session_id is already described as a UUID from data_session_open. The description adds little beyond reinforcing that this tool should be used 'after data_session_open', so it does not meaningfully expand on the schema.

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 states a specific action and resource: obtain per-query access to live data listings, with a concrete listing and price. However, it does not explicitly distinguish itself from sibling tools like data_session_fund or data_session_attach_escrow, and the word 'Buy' is ambiguous given the tool actually returns fund instructions.

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 clear sequencing: use data_preview for a free taste first, then call this after data_session_open. It does not explicitly state when not to use the tool or mention the downstream data_session_fund step, but the context is clear enough for basic routing.

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