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

Discloses the paid nature, per-query cost, maximum query count, and mentions a purchase-gate 409 error, but leaves side effects such as session creation, payment mechanics, and the role of open_tx_hash/proof_escrow_id implicit.

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?

Front-loaded purpose and clear paragraphs, but includes lengthy implementation details about REST subclassing, pydantic override, and mypy type ignores that are not relevant to an agent selecting or invoking the tool.

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?

Explains the overall paid session workflow and required relationship between listing identifiers, but does not fully cover what happens after opening, what open_tx_hash and proof_escrow_id are for, or what successful output looks like.

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?

Descriptions and prose clarify listing_id vs listing_slug (exactly one) and buyer_address defaulting to the caller's wallet, but open_tx_hash, max_queries, and proof_escrow_id lack individual semantic explanations, leaving 50% of parameters only partially described.

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 the core action 'open a data session' to buy per-query access to live data listings, and distinguishes it from the sibling tools data_preview, data_session_fund, and data_session_query by describing the open-then-fund-then-query sequence.

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 clear workflow guidance: use data_preview for a free sample, open a prepaid session, then fund and query. It could be more explicit about when not to use this tool relative to data_session_attach_escrow or data_session_fund, but the intended sequence is evident.

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