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

Annotations provide no safety hints (all false), so the description carries the burden. It discloses the cost (0.01 USDC/query), a per-session query cap (max 20), and the prepaid/fund/query sequence. However, it does not state that opening a session is a state-changing operation, whether authentication or wallet signatures are needed, or what side effects occur, leaving important behavioral gaps.

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 with the core action ('Buy per-query access'), then adds the specific listing details and the follow-up flow. Every sentence contributes useful information without excessive padding, though the listing details could be shortened.

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 tool with 6 optional parameters, no output schema, and no behavioral annotations, the description gives the cost, session limit, and a sense of the flow, but omits return values, how to provide payment/escrow proof (open_tx_hash, proof_escrow_id), and the exact-one listing requirement (though the schema documents that). It is adequate but not complete.

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?

With 50% schema description coverage, the description adds some value by naming the specific listing (quantawatch) and cost/limit, which helps fill listing_id/slug and max_queries. But it does not explain open_tx_hash, proof_escrow_id, or buyer_address, and only partially compensates for the schema's gaps.

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 (open a prepaid session) and resource (per-query access to a specific listing, quantawatch). It distinguishes from data_preview via 'first taste free via data_preview' and implies separate fund/query steps. However, 'Buy per-query access' slightly conflates the purchase with the session-opening action, so it isn't a perfect 5.

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 explicitly names data_preview as the free alternative ('first taste free via data_preview') and outlines the expected flow ('Open a prepaid session, then fund and query'). This gives clear context for when to use the tool, though it doesn't explicitly enumerate all sibling alternatives like data_session_fund or data_session_query.

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