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

Annotations only indicate readOnlyHint=false (not read-only), destructiveHint=false, etc., leaving behavioral disclosure to the description. The description adds cost information (0.01 USDC per query) and a session limit (max 20 queries/session), but does not explicitly state that the operation deducts funds from the session balance, nor does it describe failure modes (e.g., insufficient funds). It also doesn't mention idempotency or side effects beyond payment. This is partial transparency, adequate but not comprehensive.

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 two sentences long, front-loads the core purpose, and includes the pricing and sequence efficiently. It avoids redundancy and wastes no words, though it could be slightly more structured (e.g., separating the listing details from the workflow), but overall it is appropriately concise.

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 query tool with no output schema, the description is incomplete. It doesn't explain what the query returns, the role of the 'k' parameter, how delivery_receipt or sandbox_receipt affect the transaction, or the exact format of the response. It also doesn't mention any error conditions or prerequisites beyond the sequence. Given the tool's complexity (5 parameters, paid access, session-based), the description leaves many essential details unstated.

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 low (40% per signal, meaning many parameters lack descriptions). The tool description does not explain any of the parameters—it mentions the session sequence but not the meaning of 'query', 'k', 'sandbox_receipt', or 'delivery_receipt'. The schema provides descriptions for session_id, sandbox_receipt, and delivery_receipt, but query and k have no descriptions, and the tool description fails to fill that gap. The description adds no parameter semantics beyond what the schema already offers.

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's purpose: 'Buy per-query access to live data listings' – a specific verb (buy/query) and resource (data listings). It differentiates from sibling tools by naming data_preview as the free alternative and explicitly listing the session sequence (data_session_open → data_session_fund → data_session_query), making it unambiguous which step this is.

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 provides explicit usage guidance: 'first taste free via data_preview' tells when to use the free option, and the sequence 'data_session_open → data_session_fund → data_session_query' defines the prerequisite steps. It also includes the listing specifics (cratewatch at 0.01 USDC per query, max 20 queries/session), which helps the agent decide if this tool is appropriate.

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