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

With all four annotations false, the description carries the burden of behavioral disclosure and does reveal the essential traits: this is a paid transaction (0.01 USDC/query), prepaid, capped at 20 queries/session, and part of a fund-then-query flow. It does not warn about non-idempotent behavior (idempotentHint=false implies a double open could create another session) or mention any escrow prerequisites.

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 with zero filler: the purpose, price, listing name, query cap, free-preview alternative, and workflow sequence all earn their place, and the most decision-relevant facts (cost and cap) are front-loaded.

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 tool with no output schema and six optional parameters, the missing response shape is a real gap, and the semantics of open_tx_hash and proof_escrow_id are left to inference. The rich schema-level description backfills slug-vs-UUID and buyer_address defaults, which keeps this at minimum viable rather than lower.

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 itself already documents listing_id, listing_slug, and buyer_address including the exactly-one constraint and wallet default, and the description adds session-limit context for max_queries via the 20-query cap. However, at 50% schema coverage, open_tx_hash and proof_escrow_id remain unexplained in both the schema and the description, leaving an agent unable to determine their meaning.

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 identifies a specific operational action — opening a prepaid session for the govulnwatch listing — and explicitly distinguishes it from the free data_preview path ('first taste free via data_preview'). It falls short of 5 because the lead sentence 'Buy per-query access to live data listings' frames the action commercially rather than operationally, leaving the boundary with data_session_fund implicit until the closing workflow sentence.

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?

It names data_preview as the free alternative and lays out the sequence 'Open a prepaid session, then fund and query,' signaling to an agent that this is step one before data_session_fund and data_session_query. It lacks explicit when-not-to-use guidance and says nothing about the escrow path, even though data_session_attach_escrow is a sibling and proof_escrow_id is a parameter.

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