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

Annotations only say the operation is not read-only, not idempotent, and not destructive; the description adds meaningful context: cost per query, a 20-query session cap, prepaid nature, and the required fund-then-query flow. It does not mention wallet/auth requirements or response behavior, but the financial side effects are disclosed.

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?

Two sentences and front-loaded with the core value proposition and price. Nested parentheticals and the 'Listing:' fragment make it slightly less clean than it could be, but no sentence is wasted.

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 paid session opener with 6 optional params and no output schema, the description covers purpose, price, sequence, and the preview alternative. It omits the return value/session identifier and the undocumented payment/escrow params, so an agent may still be unsure how to handle open_tx_hash or proof_escrow_id.

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 descriptions cover only 3 of 6 parameters; max_queries, open_tx_hash, and proof_escrow_id are undocumented. The description mentions a query cap and billing, but it does not explain how to supply the listing, what max_queries means, or what open_tx_hash/proof_escrow_id are for, 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?

States a clear action: open a prepaid session to buy per-query access to a specific live listing. It also distinguishes itself from data_preview ('first taste free') and from later steps ('then fund and query'), so the agent can tell it apart from siblings.

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?

Gives an explicit usage path: preview free via data_preview, open the paid session here, then fund and query. It does not spell out negative cases or when to prefer data_session_attach_escrow or data_session_funding_package, but the core alternative and sequence are clear.

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