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

It discloses commercial side effects—0.01 USDC per query and a maximum of 20 queries per session—which is relevant behavioral context beyond the annotations' readOnlyHint=false. This rate and quota information helps the agent understand the operation will consume balance and has limits. It does not mention failure modes, but the annotations already cover the mutation profile, so this is acceptable.

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 with the main purpose, followed by a specific listing and the required sequence. Every fragment carries useful information and there is no filler. It is appropriately sized for a tool with this level of complexity.

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 provides valuable workflow context and pricing, but for a tool with 5 parameters and no output schema, it leaves important details unspecified. The agent is not told what a valid query looks like, what optional parameters like 'k' or 'delivery_receipt' do, or what the response will contain. It relies too heavily on parameter names and partial schema descriptions.

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 description adds little parameter-level meaning. It does not explain what the 'query' string should contain, what 'k' controls, or what 'delivery_receipt' is for. With most parameter semantics left to the schema or inference, the description fails to compensate for the low coverage.

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 the tool's role as 'Buy per-query access to live data listings' and provides a concrete listing and price, making the action discernible. It stops short of explicitly saying 'run a query', but the sequence ending in data_session_query and the cost-per-query language make the purpose clear. It also distinguishes itself from data_preview by mentioning 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?

The description explicitly prescribes the order data_session_open → data_session_fund → data_session_query, which tells an agent when this tool is meant to be used. It also points to data_preview as the free alternative. It does not discuss negative cases like unfunded sessions, but the core routing guidance is unambiguous.

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