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

Annotations cover read-only, destructive, open-world, and idempotency hints. The description adds meaningful behavioral context beyond those: this operation purchases paid access, costs 0.01 USDC per query, and platform-executes the funding. This clarifies a significant side effect that annotations alone do not convey.

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 compact and front-loaded with the core action and cost. Both sentences earn their place, and the workflow cues are integrated without redundancies or filler.

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 plus the schema and annotations are nearly sufficient for a simple one-parameter tool. It tells the agent what action to take, the cost, and the next step. It could be slightly more complete by explicitly stating that a session must already be opened, though this is already conveyed in the parameter description.

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?

There is only one parameter, session_id, and the schema description covers it fully by explaining it as a UUID from data_session_open. The description adds no extra parameter semantics, but the schema already provides sufficient meaning, so the baseline of 3 applies.

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's function: buying per-query access to live data listings, and names a specific listing with pricing. It also positions the tool relative to data_preview and data_session_query. However, it does not explicitly distinguish itself from sibling funding-related tools like data_session_funding_package or data_session_attach_escrow.

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 useful workflow context: try data_preview for free, use this tool to buy access, then use data_session_query. This helps an agent know when to invoke it. It does not, however, state when not to use it or how it compares to other funding/attachment sibling tools.

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