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

The annotations are all negative hints and disclose no side effects, so the description carries the burden. It discloses the paid, prepaid nature ('0.01 USDC per query'), a rate limit ('max 20 queries/session'), and the required session lifecycle. This is exactly behavioral context an agent needs before invoking a money-consuming query tool.

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 short sentences pack purpose, pricing, listing, limit, and sequence without filler. Key behavioral information is front-loaded before operational details.

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 is adequate for knowing when and why to call the tool, and it identifies the data listing and cost. However, with no output schema and low parameter coverage, it leaves response format, query syntax, and optional param semantics unexplained, so an agent will need to infer these from elsewhere.

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 only 40% schema description coverage, the description needed to compensate, but it does not explain the meaning of query, k, delivery_receipt, or sandbox_receipt. It adds general context about live listings but no parameter-level guidance beyond what the schema already provides.

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 identifies a specific action, 'Buy per-query access to live data listings', and the schema description clarifies it as 'Run a prepaid query against a funded data session'. It names the exact listing (hnfrontpage) and separates itself from siblings like data_preview, data_session_open, and data_session_fund, so an agent knows this is the querying step.

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?

It provides an explicit sequence — data_session_open → data_session_fund → data_session_query — telling the agent exactly when this tool is valid, and names data_preview as the free alternative for a first taste. This is clear usage guidance beyond what the schema provides.

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