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

Annotations are all false and provide no safety or behavioral hints, so the description carries the burden. It adds meaningful context by disclosing that this is a paid purchase ('Buy per-query access'), that the session is prepaid, and that there is a pricing/rate limit ('0.01 USDC/query (max 20 queries/session)'). This goes well beyond what the annotations state and does not contradict 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 short and front-loaded with the core purpose, then gives a concrete listing example and cost, then the workflow. Every sentence adds some information, though the listing-specific details could have been presented more compactly. Overall it is well structured for an agent to scan.

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?

With five parameters, no output schema, and unhelpful annotation flags, the description does not provide enough context for a complete invocation. It omits the required buyer_address parameter and the optional blockchain/escrow parameters, and it doesn't explain how the returned session would be used besides a vague 'then fund and query.' The presence of sibling tools for escrow, funding, and querying suggests a more explicit workflow would be valuable.

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 0%, so the description must compensate, but it only loosely implies listing_id via the npmwatch listing and max_queries via 'max 20 queries/session.' It doesn't explain the required buyer_address or the optional open_tx_hash and proof_escrow_id parameters. An agent cannot reliably map the description to all five schema properties.

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 and open a prepaid data session. It also distinguishes the tool from data_preview by noting that the first taste is free there, and from funding/querying tools by saying 'open a prepaid session, then fund and query.' The resource and workflow are identifiable, though the description is tightly coupled to a single listing example.

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?

It gives a clear when-to-use signal: use data_preview for a free first taste, otherwise open a prepaid session here. The phrase 'then fund and query' also implies subsequent steps, though it doesn't explicitly name sibling tools like data_session_fund or data_session_query. This is better than nothing but lacks explicit exclusions.

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