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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds meaningful context: it returns fund instructions rather than executing a payment, mentions the specific listing and cost, and clarifies the dependency on data_session_open. This goes beyond what the annotations alone communicate.

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 compact sentences deliver purpose, alternative, specific listing, pricing, and return behavior with no filler. The most important information is front-loaded and every phrase adds value.

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?

Given the tool's low complexity, rich annotations, and single documented parameter, the description covers the essential workflow, the cost, and what to expect as a result. It is somewhat vague about the contents of the 'fund instructions' return value, but this is a minor gap without an output schema.

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 coming from data_session_open. The description reinforces the session dependency but does not add substantial new meaning beyond what the schema already provides, 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 buys per-query access to live data listings and identifies the specific listing and price. It distinguishes itself from data_preview by marketing it as a free first taste, but it does not explicitly differentiate from sibling tools like data_session_fund 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 implies the workflow: preview free via data_preview, open a session, then call this tool to obtain fund instructions. However, it does not explicitly state when to choose this tool over data_session_fund or other funding-related siblings, leaving some inference required.

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