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

Annotations are sparse, so the description carries the behavioral burden. It discloses that this is a paid, prepaid operation with a specific cost per query and a maximum of 20 queries per session. This meaningfully adds financial and session-limit context beyond readOnlyHint=false.

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 short and every sentence earns its place: purpose, listing/price, and required sequence. It front-loads the key distinction from data_preview and avoids unnecessary fluff.

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 paid query tool with five parameters, no output schema, and low schema coverage, the description is incomplete. It does not explain the delivery_receipt or sandbox_receipt flow, the meaning of k, or what a successful query returns. The session sequence and pricing are helpful, but too much behavior remains undocumented for an agent to invoke this tool with full confidence.

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%, and the tool description does not explain the query, k, or delivery_receipt parameters. The only parameter-related guidance comes from the schema itself for session_id and sandbox_receipt. The description's pricing and session-limit notes do not compensate for the missing semantics of the remaining parameters.

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 identifies the operation as buying per-query access to live data listings and pairs it with a concrete listing and price. The schema description clarifies that the actual action is running a prepaid query against a funded data session. It is clear enough, though the first sentence slightly merges the buying/funding concept with the query action.

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 gives an explicit sequence (data_session_open → data_session_fund → data_session_query), which tells the agent when this tool is appropriate. It also points to data_preview as the free alternative for a first taste. It does not mention other alternatives like data_session_attach_escrow, but the core routing is clear.

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