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

The description discloses the purchase/cost nature of the operation, the need for authentication, attestation of hits, a purchase receipt, and the sandbox_receipt behavior. This meaningfully extends the annotations, which only provide non-read-only and non-destructive hints.

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?

Every sentence earns its place: the core action, free preview alternative, authentication requirement, result/receipt behavior, sandbox option, guest restriction, and REST endpoint are all packed in without redundancy. The most important semantic is front-loaded.

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?

The description covers authentication, funding prerequisite, result type, and REST path, but with no output schema and two weakly documented parameters (k and delivery_receipt), it is not fully complete for an agent expected to invoke the tool correctly. The description is strong but leaves meaningful param behavior unspecified.

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 40%, so the description must compensate for undocumented parameters. It does explain sandbox_receipt and implies session_id semantics, but k and delivery_receipt are not meaningfully described in the tool description, leaving gaps the schema alone does not fill.

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 verb and resource: 'Buy per-query access to live data listings' and 'Run a prepaid query against a funded data session'. It also differentiates from the sibling data_preview by noting the first taste is free, making the purpose unmistakable.

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 clearly establishes prerequisites: an agent API key, a funded data session, and non-guest access. It points to data_preview for a free alternative, though it does not exhaustively enumerate when not to use this tool relative to all siblings.

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