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

Annotations already indicate the tool is not read-only, and the description adds critical financial behavior: per-query cost of 0.01 USDC and a max of 20 queries per session. This goes beyond annotations meaningfully, though it does not mention failure/refund behavior or receipt/signature edge cases.

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-loaded: it states the core paid-query purpose, names the specific listing and price, and gives the prerequisite sequence in two sentences. No filler or redundant restatement of the schema.

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, non-idempotent tool with five parameters and no output schema, the description is incomplete. It omits what `query` should contain, what `k` controls, how delivery_receipt/sandbox_receipt are used, and what the agent should expect in the response. The sequence and pricing are helpful, but actual invocation still requires substantial inference.

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%, and the tool description adds almost nothing about the parameters. Session_id and sandbox_receipt are covered in the schema, but k and delivery_receipt remain unexplained, and the description does not help an agent understand what values to provide for query or k.

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 clearly states the tool is for paid per-query access to a specific live data listing, names the listing and price, and contrasts with the free data_preview sibling. It is slightly indirect about the actual execution ('Buy per-query access' rather than 'Run a query'), but the schema description 'Run a prepaid query against a funded data session' removes the ambiguity.

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 provides the required sequence (data_session_open → data_session_fund → data_session_query) and directs users to data_preview for a free first taste. This clearly tells an agent when and how to use this tool relative to its siblings.

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