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

The description says 'Returns fund instructions' which aligns with the readOnlyHint=true annotation (no actual transaction is performed). It does not contradict the annotations, nor does it add significant detail beyond what the annotations already imply about side effects.

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 concise and well-structured, using two sentences to convey the purpose, the specific listing, the price, and the relation to other tools. No superfluous words or redundant details.

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 tool's simplicity (one parameter, no output schema), the description covers the core functionality and timing. However, it fails to distinguish itself from the sibling data_session_fund, creating potential ambiguity about the exact role this tool plays in the 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?

The schema description covers 100% of the parameter (session_id) and clearly states it is a UUID from data_session_open. The description does not add any additional semantic information about the parameter beyond what is already in the schema, so the baseline score 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 function: buying per-query access to live data listings, with a specific example (showhnwatch) and price. It also mentions the relationship to data_preview and data_session_open, making the purpose unambiguous.

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 mentions using data_preview for a free taste and that it returns fund instructions after data_session_open, but it does not differentiate this tool from the sibling data_session_fund, which likely has a similar or overlapping purpose. An agent could be confused about which tool to use for funding a session.

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