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

The description discloses that this is a paying action ('USDC/query'), that it is platform-executed, and that funding enables subsequent queries. Given annotations already mark it non-read-only and non-destructive, the description adds meaningful billing/workflow transparency without contradicting the annotations.

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 tool's core purpose is front-loaded in the first sentence, followed by a concrete listing example and the free-preview pointer. The wording is compact and scannable, though the inline listing format is slightly dense.

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 single-parameter tool with no output schema, the description explains the action, the cost model, a concrete listing, and the follow-up query step. An agent has enough context to invoke it correctly with a session ID from data_session_open.

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 input schema fully documents session_id as the UUID from data_session_open, and the description reinforces workflow by referencing data_session_query. Since schema coverage is 100%, the description does not need to add much; it adds no new parameter-level detail.

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 names a specific action ('Buy per-query access') and a concrete resource (a funded data session), and it situates the tool relative to data_preview and data_session_query. It is clear, though it does not explicitly distinguish itself from sibling funding tools like data_session_attach_escrow.

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 useful workflow context: try data_preview first for free, then fund the session so data_session_query can be used. It does not state when not to use the tool or compare against related funding alternatives, but the practical context is clear.

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