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

Annotations already establish non-read-only, idempotent, non-destructive, sandbox behavior. The description adds useful context beyond annotations: per-query pricing (0.01 USDC/query), free preview access, and that funding is platform-executed rather than manually handled.

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: it states the purchase model, names the listing and price, then explains preview and downstream query usage. Every sentence contributes to tool selection or invocation context.

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 one-parameter funding mutation with no output schema and annotations covering safety, the description provides enough context: price, free preview path, platform execution, and downstream query readiness. It could say more about post-funding session state, but the essential call context is present.

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 single session_id parameter has 100% schema description coverage and is fully documented in the schema as a UUID from data_session_open. The description does not add meaning beyond the schema, so the baseline of 3 is appropriate.

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?

States a specific action ('Buy per-query access') and resource ('live data listings') and names the listing statwatch. It distinguishes itself from data_preview and data_session_query, though it does not explicitly say it funds the session referenced by session_id.

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?

Gives clear usage context: use data_preview for a free first taste, then this tool to enable data_session_query. It does not mention when to use this versus sibling funding tools like 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.