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

The description adds useful behavioral context that annotations lack: per-query pricing (0.01 USDC/query), a session cap (max 20 queries/session), and the open-then-fund sequence. However, it does not clarify side effects such as whether opening creates an on-chain transaction or requires proof_escrow_id/open_tx_hash, leaving ambiguity for a financial tool.

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: purpose comes first, and the workflow is in one final clause. The embedded listing details (arstechnicawatch / pricing) are somewhat niche and not essential, but they do not seriously distract.

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 6-parameter, no-output-schema purchase tool, the description omits too much: the roles of open_tx_hash and proof_escrow_id, what a successful open returns, and how to identify the session for later funding/querying. It gives only the high-level lifecycle.

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?

With 50% schema coverage, the description needed to explain the undocumented parameters (max_queries, open_tx_hash, proof_escrow_id). It only mentions a listing-specific query price/cap and does not add meaning to these parameters, so it fails to compensate for the coverage gap.

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 and object: 'Buy per-query access to live data listings' and 'Open a prepaid session.' It also contrasts with the free preview via data_preview, which helps orientation, though it does not explicitly differentiate data_session_open from data_session_fund or data_session_query.

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 phrase 'first taste free via data_preview' names an alternative path, and 'Open a prepaid session, then fund and query' gives a clear step in the workflow. It does not spell out explicit when-not-to-use conditions, but the intended context is evident.

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