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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive operation, so the safety profile is covered. The description adds real value by disclosing that access is prepaid and priced per query, but it does not warn that repeated calls are not idempotent (duplicate sessions) or explain what a successful open returns to be used for funding.

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?

It is short and front-loads the workflow instruction, but the middle sentence is a hardcoded, deeply nested parenthetical ('0.01 USDC/query (max 20 queries/session)') tied to one specific listing, which is a staleness risk and clutters the core message.

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 6-parameter, no-required-parameter tool with annotations and no output schema, the description covers the business flow and pricing but omits how the listing is identified, what the session handle/return is, and any funding prerequisite. Adequate to start the workflow but not self-sufficient.

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 only 50%, and the description supplies no parameter guidance at all: it never mentions listing_slug vs listing_id (exactly-one rule), max_queries bounds, buyer_address defaulting, or the escrow/tx-hash fields. The schema covers half the parameters, but the description does nothing to compensate for the other half.

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 concrete verb and resource: opening a prepaid session for per-query access to a data listing, and names the follow-up flow (fund, query). It implicitly separates itself from data_preview (free taste) and the fund/query siblings, though it never names the counterpart tools directly, keeping it short of a 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 gives both a routing condition ('first taste free via data_preview') and a sequencing instruction ('Open a prepaid session, then fund and query'), which tells the agent where this step sits in the workflow. There is no explicit when-not-to-use case or prerequisite statement (e.g. that funding must follow before querying works).

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