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

Annotations declare only that the tool is not read-only, not idempotent, and not destructive. The description adds valuable behavioral context by disclosing the per-query cost (0.01 USDC) and the hard cap of 20 queries per session, which an agent needs to predict charges and limits. No contradiction with annotations.

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: three sentences that front-load the core purpose, then provide a concrete pricing/limit example, then the workflow sequence. The specific deepmindwatch listing is somewhat incidental, but nothing is redundant or bloated.

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 gives the essential workflow (open → fund → query), pricing, quota, and the free-preview route, which is good contextual scaffolding. However, with no output schema, it does not state what a successful query returns, nor does it clarify the k parameter or delivery receipt behavior. It is adequate but leaves notable gaps for an agent invoking a paid data API.

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?

With schema description coverage at only 40%, the description carries the burden of explaining parameters, but it does not. The parameters query and k are undocumented in both schema and description, and the description does not explain delivery_receipt or sandbox_receipt beyond the schema. Pricing and session quota are behavioral facts, not parameter semantics.

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 states a clear action: buying per-query access to live data listings, and identifies this tool as the paid counterpart to data_preview. The sequence line defines it as the final query step after opening and funding a session. It is specific enough to distinguish from siblings, though the phrasing 'buy per-query access' is a bit indirect for a query operation.

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 explicitly names data_preview as the free alternative ('first taste free via data_preview') and gives the required workflow sequence 'data_session_open → data_session_fund → data_session_query'. This tells an agent when to use this tool relative to key siblings, though it does not spell out conditions such as 'do not use before funding' in explicit terms.

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