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

Annotations already convey that it's not read-only (readOnlyHint=false) and not destructive (destructiveHint=false), but the description adds value by explaining that it executes funding on-platform. The description doesn't mention any side effects like payment deduction or balance requirements, but given the annotations cover safety, a 3 is appropriate.

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 key action. It includes promotional language ('first taste free') that is marginally useful for usage context, and it's structured as a single sentence that conveys the core function efficiently. A small deduction for the slightly colloquial phrase 'first taste free' which could be considered non-essential.

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?

Given the simple single-parameter input and the presence of sibling tools that handle other steps (open, query, funding packages), the description is sufficiently complete for an agent to call it correctly. It identifies the target (cratewatch listing) and the pricing, and the reference to data_session_query implies the next step. No output schema exists, so no return value explanation is required, though the agent might wonder about the response format.

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?

The schema coverage is 100%, as the session_id parameter is fully documented in the description. The description doesn't add extra detail beyond what the schema provides, so the baseline 3 is appropriate; it doesn't harm but doesn't add value.

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: buying per-query access to live data listings for a specific data session. It mentions the specific listing and price, and distinguishes it from the free preview tool (data_preview) and the query tool (data_session_query). However, it doesn't explicitly differentiate itself from the sibling funding tools (data_session_funding_package, data_session_attach_escrow), though the mention of 'platform-executes funding' hints at a different mechanism.

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 provides context: use it after opening a session (implied by 'data_session_query' and the session_id parameter) and mentions the free preview as an alternative first step. However, it doesn't explicitly state when NOT to use it versus data_session_funding_package or data_session_attach_escrow, leaving some ambiguity.

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