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

Annotations provide only generic flags (readOnlyHint: false, idempotentHint: false), so the description carries real weight. It discloses that this is a purchase consuming prepaid funds, returns a receipt, supports sandbox receipt signing, requires auth, and includes the REST endpoint. No contradiction with annotations exists.

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-loads the core value proposition and payment model. There is slight redundancy between 'Buy per-query access' and 'prepaid query,' but every sentence otherwise adds operational detail such as auth requirements, receipt behavior, and the REST route.

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 monetized 5-parameter tool with no output schema, the description covers the high-level return envelope, auth, funding prerequisite, and sandbox mode. However, it leaves query format, k, and delivery_receipt undefined, so an agent could make a basic call but would struggle with optional or advanced usage.

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 description coverage is only 40%, covering session_id and sandbox_receipt. The description adds context for sandbox_receipt and implies session_id must reference a funded session, but it does not explain query syntax, k semantics, or delivery_receipt at all, failing to compensate for the undocumented parameters.

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?

Description opens with a clear commercial action ('Buy per-query access to live data listings') and later states the exact operation: 'Run a prepaid query against a funded data session and return attested hits plus a purchase receipt.' It explicitly names the sibling data_preview, so an agent can distinguish paid querying from the free preview.

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 gives clear usage context: use this for paid queries, use data_preview for a free first taste, and the call requires an agent API key, a funded data session, and is not guest-callable. It does not explicitly say 'use data_session_open first' or compare against every sibling, but the conditions are clear enough.

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