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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false. The description adds behavior the annotations can't express: per-query cost (0.01 USDC), a 20-queries/session cap, and the requirement of a funded prepaid session. It does not restate non-idempotency in words, so not a full 5.

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 dense sentences, front-loaded with the core purpose before pricing and the sequence. Every clause carries information (cost, limit, prerequisites, alternative), though the listing-detail sentence is a bit compressed.

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 no output schema, the description covers cost model, session cap, prerequisites, and the free preview alternative, which is nearly everything an agent needs. It stops short of saying what a successful query returns, but the pricing/sequence context makes it callable correctly.

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 coverage is only 40% across 5 params, and the description adds no detail on k, sandbox_receipt, or delivery_receipt. It does clarify what the query targets (the awswhatsnew listing) and implies session_id via the sequence, but the numeric/optional params remain solely dependent on the schema.

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 and resource ('Buy per-query access to live data listings') and names the exact listing served (awswhatsnew). It distinguishes itself from siblings by pointing to data_preview for the free path and by spelling out the open → fund → query sequence.

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?

Explicitly gives the prerequisite chain (data_session_open → data_session_fund → data_session_query) and names data_preview as the free alternative, so the agent knows the setup required and where to go for a no-cost taste. No explicit 'when not to use' beyond that, keeping it at 4.

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