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

Beyond the minimal annotations (all false hints), the description discloses meaningful behavioral traits: this is a paid purchase, sessions are prepaid, there is a per-query cost and a per-session query cap, and funding/querying must happen afterward. It does not cover idempotency, on-chain transaction effects, or what happens when optional fields like open_tx_hash or proof_escrow_id are provided, but the core behavior is transparent.

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 front-loaded with the core purpose before the listing-specific example. The pricing and cap details earn their place because they inform the caller of cost and limits. Slight clutter from the inline listing snippet keeps it from being perfectly structured, but there is no wasteful filler.

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?

With five parameters, no output schema, and no parameter descriptions, the description leaves important gaps: how to determine buyer_address, the meaning and format of open_tx_hash and proof_escrow_id, and what the tool returns. It gives useful workflow context but is not complete enough for an agent to invoke it reliably on arbitrary listings or handle optional fields correctly.

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?

Schema description coverage is 0%, so the description bears full responsibility for explaining parameters, but it only indirectly hints at listing_id (via the quakewatch example) and max_queries (via the 20-query cap). Required buyer_address is not explained, and optional fields open_tx_hash and proof_escrow_id are entirely absent. This is insufficient for a 5-parameter tool with no schema descriptions.

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 action ('Buy per-query access to live data listings', 'Open a prepaid session') and names the exact resource. It also distinguishes itself from data_preview by offering the paid 'taste' alternative. The tool's purpose is unambiguous even without the title.

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 explicitly points to data_preview as the free first-taste alternative and positions data_session_open as the required first step before funding and querying. It gives clear context for when to use this tool, though it does not spell out formal when-not conditions or name all sibling session tools.

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