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

The description adds behavior not present in the annotations: 'Platform-executes funding' discloses that this operation automatically handles the payment/funding mechanism, and the 0.01 USDC/query cost gives the agent an expectation of financial impact. This complements the annotations (readOnlyHint=false, idempotentHint=true) without contradicting them, though it leaves details like payment method unstated.

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 in the first clause. The inline use of 'data_session_query' as a verb and the single-line listing example are slightly awkward but informative, and every sentence contributes purpose, cost, or sequencing.

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 simple one-parameter tool, the description covers the main workflow (preview -> fund -> query) and includes pricing, while the schema and annotations handle session provenance and safety profile. It could be more complete by explicitly stating that the session must already be open and by contrasting with data_session_funding_package, but nothing essential is missing for selection and invocation.

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 schema already documents session_id 100% as 'UUID of a data session you opened (from data_session_open)', so the description adds little parameter-level meaning. The listing and cost context explain what is being funded but not how to obtain or validate session_id; this is adequate because schema coverage is high.

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 action as 'Buy per-query access to live data listings' and ties it to funding and subsequent querying via 'so you can data_session_query'. It distinguishes itself from data_preview by calling preview free, but it does not explicitly say 'add funds to an existing data session', which is the actual operation implied by the session_id parameter.

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 provides a clear usage flow: start free with data_preview, then fund, then call data_session_query. It names data_preview as the alternative for a free first taste, but it does not explicitly differentiate this per-query funding tool from the sibling data_session_funding_package or state when not to use it.

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