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

Annotations only indicate non-read-only and non-idempotent behavior; the description adds meaningful economic and rate context: 0.01 USDC per query, max 20 queries/session, and a specific live listing. It does not describe receipt handling or balance deduction side effects in detail, but the core paid side effect is clear.

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 dense sentences cover the action, free alternative, listing, price, rate limit, and required sequence. The essential action is front-loaded and there is no filler.

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 covers the session lifecycle and pricing well enough for basic invocation, but there is no output schema and the description does not state what a successful query returns. It also leaves optional receipt/`k` parameters unexplained, so non-default paths are underspecified.

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%, so the description carries extra responsibility for parameter meaning. It does not explain `k`, `delivery_receipt`, or how `query` should be phrased; it references `session_id` only indirectly through the session sequence. This leaves several parameters under-defined for an agent.

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 schema description states 'Run a prepaid query against a funded data session,' and the main description anchors it in the sequence `data_session_open → data_session_fund → data_session_query`. This clearly identifies the verb, resource, and distinguishes it from the free `data_preview` alternative.

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 contrasts paid per-query access with 'first taste free via data_preview' and gives the required preceding sequence. An agent can confidently decide when to call this tool versus data_preview or the earlier session setup tools.

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