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

Annotations already indicate readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful behavioral context by specifying that the tool returns fund instructions rather than performing an actual transfer, and it discloses the specific cost per query. The word 'Buy' is slightly misleading but is reconciled by 'Returns fund 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?

Two sentences deliver the core purpose, pricing, free-preview alternative, prerequisite, and return behavior without wasted words. The most important information is front-loaded and the listing is specified compactly.

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 single-parameter tool with read-only annotations, the description is mostly complete: it names the session prerequisite, the return type, and the free alternative. However, because there is no output schema and the term 'fund instructions' is not further explained, an agent may not know how those instructions connect to data_session_fund or data_session_attach_escrow.

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 only parameter session_id is fully described in the schema as a UUID from data_session_open, so schema coverage is 100%. The description reinforces the prerequisite but adds no new semantic detail about the parameter beyond what the schema already provides, so the baseline of 3 is appropriate.

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 tool provides per-query paid access to a specific live listing and identifies the exact listing and price. It references data_preview and data_session_open, but does not clearly differentiate itself from the sibling data_session_fund or data_session_attach_escrow, leaving some ambiguity about whether this tool executes the purchase or merely packages the funding instructions.

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 implies the tool should be used after data_session_open and mentions data_preview as a free alternative. However, it does not explicitly state when to use this tool instead of data_session_fund, data_session_attach_escrow, or data_session_query, so the routing among related session tools remains partially implicit.

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