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

Annotations declare readOnlyHint=false, idempotentHint=false, openWorldHint=false, but the description doesn't elaborate on the mutating/consumptive nature of the call. It embeds pricing (0.01 USDC) and a max 20 queries/session cap, which is useful behavioral context, but doesn't explain what a query actually returns, whether the session is charged on failure, or how prepaid balance is consumed.

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 concise sentences: purpose, listing detail, sequence. Front-loaded with the core action, though the sequence is placed last where it would be more useful up front.

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, stateful, non-idempotent query tool with a 5-param schema (40% coverage) and no output schema, the description should explain charging behavior, session lifecycle, and key parameter meanings. It provides pricing and sequence but leaves significant functional gaps.

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 coverage is only 40%; parameters like k, delivery_receipt, and sandbox_receipt are weakly documented in the schema and not explained in the description. The description mentions no parameter syntax or meaning beyond the listing. This leaves an agent unclear on how k, receipts, or sandbox wallets affect the query.

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 a specific verb and resource — paying per-query for live data listings — and names the sequence step relative to siblings. It doesn't cleanly describe what data_session_query itself does versus data_session_fund, but the listing and per-query payment framing make the purpose clear enough.

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 an explicit prerequisite chain (data_session_open → fund → query) and points to data_preview as the free alternative. This is strong routing guidance, though it doesn't state when-not-to-use or list other alternatives.

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