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

Annotations already indicate readOnlyHint=false, destructiveHint=false, and idempotentHint=true. The description adds useful behavioral context about per-query pricing (0.01 USDC/query), that funding is platform-executed, and that this enables subsequent querying. This goes beyond what annotations provide without contradicting 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 with the core action, then gives pricing and workflow context. The specific example listing could be seen as extra detail, but it is still concise and informative.

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 tool with annotations, the description covers the main purpose and names related tools. However, it leaves the relationship with data_session_funding_package and data_session_attach_escrow ambiguous, which could cause an agent to select the wrong sibling in a multi-step funding workflow.

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?

There is only one parameter, session_id, and the schema already describes it fully as a UUID from data_session_open. The tool description adds no parameter-level meaning beyond the schema, so the baseline of 3 applies.

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 action: buying per-query access to live data listings and funding a data session so it can be queried. It references relevant siblings (data_preview, data_session_query), though it does not explicitly distinguish itself from data_session_funding_package or 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?

The description implies a workflow: try data_preview first, then fund access so you can data_session_query. However, it gives no explicit guidance on when to choose this tool over the similarly named data_session_funding_package or data_session_attach_escrow, and it does not state prerequisites such as having an open session.

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