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

The description clearly discloses that this is a paid, platform-executed funding action and even names the price (0.01 USDC/query), which is important behavioral context beyond the annotations. The annotations already signal a mutating, non-destructive, idempotent operation, and the description does not contradict them.

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 short and front-loaded: it opens with the core purpose and free-preview hook, then gives the price and follow-up path. The hardcoded listing detail adds slight clutter, but overall the text is compact and every sentence earns its place.

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, annotation-backed funding tool, the description explains the financial action and the immediate next step, and the schema covers session_id. The notable gap is lack of routing among sibling funding tools, which could lead an agent to select the wrong tool without additional reasoning.

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 covers the only parameter, session_id, with 100% coverage, including its origin from data_session_open. The description adds no parameter-level detail, but none is especially needed given that the schema already defines the meaning and provenance.

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 clear action ('Buy per-query access') and identifies the enabling next step (data_session_query), so the agent understands this is the funding step before querying. However, it does not explicitly distinguish this from sibling funding tools like data_session_funding_package or data_session_attach_escrow, and it hardcodes one specific listing and price rather than describing the generic operation.

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 workflow is implied: use data_preview for a free taste, then fund the session so you can call data_session_query. But there is no explicit when-to-use or when-not-to-use guidance relative to other data_session_* siblings, so the agent must infer when this is the right tool.

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