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

Annotations indicate readOnly, idempotent, and non-destructive behavior, and the description says it 'returns fund instructions' rather than executing a purchase, so there is no direct contradiction. However, the phrase 'Buy per-query access' could misleadingly imply an actual financial transaction rather than merely returning instructions.

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-loads the main purpose, though the phrase 'first taste free via data_preview' and the listing details add some promotional noise. Overall it is concise.

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 no output schema, the description only says 'Returns fund instructions' without detailing the structure or content of those instructions. It also does not explain how this tool differs from closely related sibling tools, leaving some contextual gaps.

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?

The single parameter session_id is described in the schema as a UUID from data_session_open, and the description reinforces that it should be used after data_session_open. The parameter meaning is clear and fully covered.

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 it buys per-query access to a specific listing and returns fund instructions, but it does not clearly define the tool's role relative to sibling tools like data_session_fund or data_session_attach_escrow. The purpose is understandable but ambiguous.

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 references data_preview and data_session_open but does not explicitly say when to use this tool instead of data_session_fund or data_session_attach_escrow. No clear usage conditions or alternatives are provided.

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