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

Annotations already declare the mutation profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false). The description adds the payment context 'Platform-executes funding,' which is useful beyond the annotations, but it omits what the funding call returns, what happens to prior funding, or whether repeat funding is a no-op.

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?

Three sentences, front-loaded with the core action, then the free-alternative cue, then the execution note. The middle listing block is tangential catalog detail, costing it a perfect score, but nothing is dangerously verbose.

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?

No output schema exists, so the description carries the burden of explaining the result of a payment/funding call, which it only gestures at ('so you can data_session_query'). It does not state the funding amount, the returned session state, or how costs are attributed — meaningful gaps for a spend-incurring tool.

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?

Only one parameter (session_id) and schema coverage is 100%, with the schema fully documenting it as a UUID from data_session_open. The description adds no syntax or constraint beyond the schema, 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?

States a specific verb (buy) and resource (per-query access to live data listings), and implicitly separates itself from data_preview (free taste) and data_session_query (what the funding enables). The embedded listing marketing (awswhatsnew, 0.01 USDC/query) is specific but reads more like catalog copy than a purpose statement, slightly blurring what the tool itself does.

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?

Gives a clear workflow cue: try data_preview first for free, then fund so you can data_session_query. Both the free alternative and the downstream tool are named. It stops short of stating when funding is NOT needed or any prerequisites for the referenced session.

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